1.Mybatis的架构
1.1 Mybatis的框架分层
1.2 MyBatis的实现原理
mybatis底层还是采用原生jdbc来对数据库进行操作的，它支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架，其主要就完成2件事情：
- 封装JDBC操作
- 利用反射打通Java类与SQL语句之间的相互转换
MyBatis的主要设计目的就是让我们对执行SQL语句时对输入输出的数据管理更加方便，所以方便地写出SQL和方便地获取SQL的执行结果才是MyBatis的核心竞争力。
它通过SqlSessionFactory，SqlSession，Executor,StatementHandler，ParameterHandler，ResultHandler和TypeHandler等几个处理器封装了这些过程
执行器：Executor(update, query, flushStatements, commit, rollback, getTransaction, close, isClosed)，是MyBatis调度的核心，负责SQL语句的生成和查询缓存的维护
参数处理器：ParameterHandler(getParameterObject, setParameters)，负责对用户传递的参数转换成JDBC Statement所对应的数据类型
结构处理器：ResultSetHandler(handleResultSets, handleOutputParameters)，负责将JDBC返回的ResultSet结果集对象转换成List类型的集合
sql查询处理器：StatementHandler(prepare, parameterize, batch, update, query)，封装了JDBC Statement操作，负责对JDBC statement 的操作，如设置参数等
Configuration：MyBatis所有的配置信息都保存在Configuration对象之中，配置文件中的大部分配置都会存储到该类中
SqlSession：作为MyBatis工作的主要顶层API，表示和数据库交互时的会话，完成必要数据库增删改查功能
TypeHandler：负责java数据类型和jdbc数据类型(也可以说是数据表列类型)之间的映射和转换
MappedStatement：MappedStatement维护一条<select|update|delete|insert>节点的封装
SqlSource：负责根据用户传递的parameterObject，动态地生成SQL语句，将信息封装到BoundSql对象中，并返回
BoundSql：表示动态生成的SQL语句以及相应的参数信
BaseBuilder：负责解析xml映射文件，生成sql语句，包括解析select|insert|update|delete|cache-ref|cache|resultMap|sql|parameterMap|namespace|where|trim|set|where|if|foreach|choose|if|when|otherwise|bind|parameterType|resultType|resultMap,该类是抽象类，它有很多子类。
其中StatementHandler用通过ParameterHandler与ResultHandler分别进行参数预编译 与结果处理。而ParameterHandler与ResultHandler都使用TypeHandler进行映射。
BaseBuilder的类图继承结构如下：
如下图：
2.Mybatis工作过程
通过读mybatis的源码进行分析mybatis的执行操作的整个过程，我们通过debug调试就可以知道Mybatis每一步做了什么事，我先把debug每一步结果 截图，然后在分析这个流程。
第一步:读取配置文件，形成InputStream：
String resource = "mybatis.xml"; // 加载mybatis的配置文件（它也加载关联的映射文件）
InputStream inputStream = null;
try {
inputStream = Resources.getResourceAsStream(resource);
} catch (IOException e) {
e.printStackTrace();
} // 构建sqlSession的工厂
sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
2.1 解析xml文件并创建SqlSessionFacotry的过程
首先会创建SqlSessionFactoryBuilder对象，然后由它进行创建SqlSessionFactory。这里用到的是建造者模式，建造者模式最简单的理解就是不手动new对象，而是由其他类来进行对象的创建。
public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) {
try {
XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
return build(parser.parse());
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error building SqlSession.", e);
} finally {
ErrorContext.instance().reset();
try {
inputStream.close();
} catch (IOException e) {
// Intentionally ignore. Prefer previous error.
}
}
}
public SqlSessionFactory build(Configuration config) {
return new DefaultSqlSessionFactory(config);
}
XMLConfigBuilder对象会进行XML配置文件的解析，实际为configuration节点的解析操作。
// XMLConfigBuilder类
public Configuration parse() {
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
} private void parseConfiguration(XNode root) {
try {
//issue #117 read properties first
propertiesElement(root.evalNode("properties"));
Properties settings = settingsAsProperties(root.evalNode("settings"));
loadCustomVfs(settings);
typeAliasesElement(root.evalNode("typeAliases"));
pluginElement(root.evalNode("plugins"));
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
reflectorFactoryElement(root.evalNode("reflectorFactory"));
settingsElement(settings);
// read it after objectFactory and objectWrapperFactory issue #631 /* 处理environments节点数据 */
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
在configuration节点下会依次解析properties/settings/.../mappers等节点配置。在解析environments节点时，会根据transactionManager的配置来创建事务管理器，根据dataSource的配置来创建DataSource对象，这里面包含了数据库登录的相关信息。在解析mappers节点时，会读取该节点下所有的mapper文件，然后进行解析，并将解析后的结果存到configuration对象中。
// XMLConfigBuilder类
private void environmentsElement(XNode context) throws Exception {
if (context != null) {
if (environment == null) {
environment = context.getStringAttribute("default");
}
for (XNode child : context.getChildren()) {
String id = child.getStringAttribute("id");
if (isSpecifiedEnvironment(id)) { /* 创建事务管理器 */
TransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));
DataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));
DataSource dataSource = dsFactory.getDataSource(); /* 建造者模式 设计模式 */
Environment.Builder environmentBuilder = new Environment.Builder(id)
.transactionFactory(txFactory)
.dataSource(dataSource);
configuration.setEnvironment(environmentBuilder.build());
}
}
}
} // 解析单独的mapper文件
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage);
} else {
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
String mapperClass = child.getStringAttribute("class");
if (resource != null && url == null && mapperClass == null) {
ErrorContext.instance().resource(resource);
InputStream inputStream = Resources.getResourceAsStream(resource);
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
mapperParser.parse(); // 开始解析mapper文件了 :)
} else if (resource == null && url != null && mapperClass == null) {
ErrorContext.instance().resource(url);
InputStream inputStream = Resources.getUrlAsStream(url);
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
mapperParser.parse();
} else if (resource == null && url == null && mapperClass != null) {
Class<?> mapperInterface = Resources.classForName(mapperClass);
configuration.addMapper(mapperInterface);
} else {
throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
}
}
}
}
}
使用类XMLMapperBuilder解析每个mapper的xml文件
public XMLMapperBuilder(InputStream inputStream, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {
this(new XPathParser(inputStream, true, configuration.getVariables(), new XMLMapperEntityResolver()),
configuration, resource, sqlFragments);
}
private XMLMapperBuilder(XPathParser parser, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {
super(configuration);
this.builderAssistant = new MapperBuilderAssistant(configuration, resource);
this.parser = parser;
this.sqlFragments = sqlFragments;
this.resource = resource;
}
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
bindMapperForNamespace();
}
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}
public XNode getSqlFragment(String refid) {
return sqlFragments.get(refid);
}
private void configurationElement(XNode context) {
try {
String namespace = context.getStringAttribute("namespace");
if (namespace == null || namespace.equals("")) {
throw new BuilderException("Mapper's namespace cannot be empty");
}
builderAssistant.setCurrentNamespace(namespace);
cacheRefElement(context.evalNode("cache-ref"));
cacheElement(context.evalNode("cache"));
parameterMapElement(context.evalNodes("/mapper/parameterMap"));
resultMapElements(context.evalNodes("/mapper/resultMap"));
sqlElement(context.evalNodes("/mapper/sql"));
buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
} catch (Exception e) {
throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
}
}
private void buildStatementFromContext(List<XNode> list) {
if (configuration.getDatabaseId() != null) {
buildStatementFromContext(list, configuration.getDatabaseId());
}
buildStatementFromContext(list, null);
}
private void buildStatementFromContext(List<XNode> list, String requiredDatabaseId) {
for (XNode context : list) {
final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId);
try {
statementParser.parseStatementNode();
} catch (IncompleteElementException e) {
configuration.addIncompleteStatement(statementParser);
}
}
}
private void parsePendingResultMaps() {
Collection<ResultMapResolver> incompleteResultMaps = configuration.getIncompleteResultMaps();
synchronized (incompleteResultMaps) {
Iterator<ResultMapResolver> iter = incompleteResultMaps.iterator();
while (iter.hasNext()) {
try {
iter.next().resolve();
iter.remove();
} catch (IncompleteElementException e) {
// ResultMap is still missing a resource...
}
}
}
}
private void parsePendingCacheRefs() {
Collection<CacheRefResolver> incompleteCacheRefs = configuration.getIncompleteCacheRefs();
synchronized (incompleteCacheRefs) {
Iterator<CacheRefResolver> iter = incompleteCacheRefs.iterator();
while (iter.hasNext()) {
try {
iter.next().resolveCacheRef();
iter.remove();
} catch (IncompleteElementException e) {
// Cache ref is still missing a resource...
}
}
}
}
private void parsePendingStatements() {
Collection<XMLStatementBuilder> incompleteStatements = configuration.getIncompleteStatements();
synchronized (incompleteStatements) {
Iterator<XMLStatementBuilder> iter = incompleteStatements.iterator();
while (iter.hasNext()) {
try {
iter.next().parseStatementNode();
iter.remove();
} catch (IncompleteElementException e) {
// Statement is still missing a resource...
}
}
}
}
private void cacheRefElement(XNode context) {
if (context != null) {
configuration.addCacheRef(builderAssistant.getCurrentNamespace(), context.getStringAttribute("namespace"));
CacheRefResolver cacheRefResolver = new CacheRefResolver(builderAssistant, context.getStringAttribute("namespace"));
try {
cacheRefResolver.resolveCacheRef();
} catch (IncompleteElementException e) {
configuration.addIncompleteCacheRef(cacheRefResolver);
}
}
}
private void cacheElement(XNode context) throws Exception {
if (context != null) {
String type = context.getStringAttribute("type", "PERPETUAL");
Class<? extends Cache> typeClass = typeAliasRegistry.resolveAlias(type);
String eviction = context.getStringAttribute("eviction", "LRU");
Class<? extends Cache> evictionClass = typeAliasRegistry.resolveAlias(eviction);
Long flushInterval = context.getLongAttribute("flushInterval");
Integer size = context.getIntAttribute("size");
boolean readWrite = !context.getBooleanAttribute("readOnly", false);
boolean blocking = context.getBooleanAttribute("blocking", false);
Properties props = context.getChildrenAsProperties();
builderAssistant.useNewCache(typeClass, evictionClass, flushInterval, size, readWrite, blocking, props);
}
}
private void parameterMapElement(List<XNode> list) throws Exception {
for (XNode parameterMapNode : list) {
String id = parameterMapNode.getStringAttribute("id");
String type = parameterMapNode.getStringAttribute("type");
Class<?> parameterClass = resolveClass(type);
List<XNode> parameterNodes = parameterMapNode.evalNodes("parameter");
List<ParameterMapping> parameterMappings = new ArrayList<ParameterMapping>();
for (XNode parameterNode : parameterNodes) {
String property = parameterNode.getStringAttribute("property");
String javaType = parameterNode.getStringAttribute("javaType");
String jdbcType = parameterNode.getStringAttribute("jdbcType");
String resultMap = parameterNode.getStringAttribute("resultMap");
String mode = parameterNode.getStringAttribute("mode");
String typeHandler = parameterNode.getStringAttribute("typeHandler");
Integer numericScale = parameterNode.getIntAttribute("numericScale");
ParameterMode modeEnum = resolveParameterMode(mode);
Class<?> javaTypeClass = resolveClass(javaType);
JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
@SuppressWarnings("unchecked")
Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
ParameterMapping parameterMapping = builderAssistant.buildParameterMapping(parameterClass, property, javaTypeClass, jdbcTypeEnum, resultMap, modeEnum, typeHandlerClass, numericScale);
parameterMappings.add(parameterMapping);
}
builderAssistant.addParameterMap(id, parameterClass, parameterMappings);
}
}
private void resultMapElements(List<XNode> list) throws Exception {
for (XNode resultMapNode : list) {
try {
resultMapElement(resultMapNode);
} catch (IncompleteElementException e) {
// ignore, it will be retried
}
}
}
private ResultMap resultMapElement(XNode resultMapNode) throws Exception {
return resultMapElement(resultMapNode, Collections.<ResultMapping> emptyList());
}
private ResultMap resultMapElement(XNode resultMapNode, List<ResultMapping> additionalResultMappings) throws Exception {
ErrorContext.instance().activity("processing " + resultMapNode.getValueBasedIdentifier());
String id = resultMapNode.getStringAttribute("id",
resultMapNode.getValueBasedIdentifier());
String type = resultMapNode.getStringAttribute("type",
resultMapNode.getStringAttribute("ofType",
resultMapNode.getStringAttribute("resultType",
resultMapNode.getStringAttribute("javaType"))));
String extend = resultMapNode.getStringAttribute("extends");
Boolean autoMapping = resultMapNode.getBooleanAttribute("autoMapping");
Class<?> typeClass = resolveClass(type);
Discriminator discriminator = null;
List<ResultMapping> resultMappings = new ArrayList<ResultMapping>();
resultMappings.addAll(additionalResultMappings);
List<XNode> resultChildren = resultMapNode.getChildren();
for (XNode resultChild : resultChildren) {
if ("constructor".equals(resultChild.getName())) {
processConstructorElement(resultChild, typeClass, resultMappings);
} else if ("discriminator".equals(resultChild.getName())) {
discriminator = processDiscriminatorElement(resultChild, typeClass, resultMappings);
} else {
List<ResultFlag> flags = new ArrayList<ResultFlag>();
if ("id".equals(resultChild.getName())) {
flags.add(ResultFlag.ID);
}
resultMappings.add(buildResultMappingFromContext(resultChild, typeClass, flags));
}
}
ResultMapResolver resultMapResolver = new ResultMapResolver(builderAssistant, id, typeClass, extend, discriminator, resultMappings, autoMapping);
try {
return resultMapResolver.resolve();
} catch (IncompleteElementException e) {
configuration.addIncompleteResultMap(resultMapResolver);
throw e;
}
}
private void processConstructorElement(XNode resultChild, Class<?> resultType, List<ResultMapping> resultMappings) throws Exception {
List<XNode> argChildren = resultChild.getChildren();
for (XNode argChild : argChildren) {
List<ResultFlag> flags = new ArrayList<ResultFlag>();
flags.add(ResultFlag.CONSTRUCTOR);
if ("idArg".equals(argChild.getName())) {
flags.add(ResultFlag.ID);
}
resultMappings.add(buildResultMappingFromContext(argChild, resultType, flags));
}
}
private Discriminator processDiscriminatorElement(XNode context, Class<?> resultType, List<ResultMapping> resultMappings) throws Exception {
String column = context.getStringAttribute("column");
String javaType = context.getStringAttribute("javaType");
String jdbcType = context.getStringAttribute("jdbcType");
String typeHandler = context.getStringAttribute("typeHandler");
Class<?> javaTypeClass = resolveClass(javaType);
@SuppressWarnings("unchecked")
Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
Map<String, String> discriminatorMap = new HashMap<String, String>();
for (XNode caseChild : context.getChildren()) {
String value = caseChild.getStringAttribute("value");
String resultMap = caseChild.getStringAttribute("resultMap", processNestedResultMappings(caseChild, resultMappings));
discriminatorMap.put(value, resultMap);
}
return builderAssistant.buildDiscriminator(resultType, column, javaTypeClass, jdbcTypeEnum, typeHandlerClass, discriminatorMap);
}
private void sqlElement(List<XNode> list) throws Exception {
if (configuration.getDatabaseId() != null) {
sqlElement(list, configuration.getDatabaseId());
}
sqlElement(list, null);
}
private void sqlElement(List<XNode> list, String requiredDatabaseId) throws Exception {
for (XNode context : list) {
String databaseId = context.getStringAttribute("databaseId");
String id = context.getStringAttribute("id");
id = builderAssistant.applyCurrentNamespace(id, false);
if (databaseIdMatchesCurrent(id, databaseId, requiredDatabaseId)) {
sqlFragments.put(id, context);
}
}
}
private boolean databaseIdMatchesCurrent(String id, String databaseId, String requiredDatabaseId) {
if (requiredDatabaseId != null) {
if (!requiredDatabaseId.equals(databaseId)) {
return false;
}
} else {
if (databaseId != null) {
return false;
}
// skip this fragment if there is a previous one with a not null databaseId
if (this.sqlFragments.containsKey(id)) {
XNode context = this.sqlFragments.get(id);
if (context.getStringAttribute("databaseId") != null) {
return false;
}
}
}
return true;
}
private ResultMapping buildResultMappingFromContext(XNode context, Class<?> resultType, List<ResultFlag> flags) throws Exception {
String property;
if (flags.contains(ResultFlag.CONSTRUCTOR)) {
property = context.getStringAttribute("name");
} else {
property = context.getStringAttribute("property");
}
String column = context.getStringAttribute("column");
String javaType = context.getStringAttribute("javaType");
String jdbcType = context.getStringAttribute("jdbcType");
String nestedSelect = context.getStringAttribute("select");
String nestedResultMap = context.getStringAttribute("resultMap",
processNestedResultMappings(context, Collections.<ResultMapping> emptyList()));
String notNullColumn = context.getStringAttribute("notNullColumn");
String columnPrefix = context.getStringAttribute("columnPrefix");
String typeHandler = context.getStringAttribute("typeHandler");
String resultSet = context.getStringAttribute("resultSet");
String foreignColumn = context.getStringAttribute("foreignColumn");
boolean lazy = "lazy".equals(context.getStringAttribute("fetchType", configuration.isLazyLoadingEnabled() ? "lazy" : "eager"));
Class<?> javaTypeClass = resolveClass(javaType);
@SuppressWarnings("unchecked")
Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler);
JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType);
return builderAssistant.buildResultMapping(resultType, property, column, javaTypeClass, jdbcTypeEnum, nestedSelect, nestedResultMap, notNullColumn, columnPrefix, typeHandlerClass, flags, resultSet, foreignColumn, lazy);
}
private String processNestedResultMappings(XNode context, List<ResultMapping> resultMappings) throws Exception {
if ("association".equals(context.getName())
|| "collection".equals(context.getName())
|| "case".equals(context.getName())) {
if (context.getStringAttribute("select") == null) {
ResultMap resultMap = resultMapElement(context, resultMappings);
return resultMap.getId();
}
}
return null;
}
private void bindMapperForNamespace() {
String namespace = builderAssistant.getCurrentNamespace();
if (namespace != null) {
Class<?> boundType = null;
try {
boundType = Resources.classForName(namespace);
} catch (ClassNotFoundException e) {
//ignore, bound type is not required
}
if (boundType != null) {
if (!configuration.hasMapper(boundType)) {
// Spring may not know the real resource name so we set a flag
// to prevent loading again this resource from the mapper interface
// look at MapperAnnotationBuilder#loadXmlResource
configuration.addLoadedResource("namespace:" + namespace);
configuration.addMapper(boundType);
}
}
}
}
解析玩xml文件之后，使用类XMLStatementBuilder创建每个sql（包括insert,update,select,delete等）语句的MappedStatement。
public void parseStatementNode() {
String id = context.getStringAttribute("id");
String databaseId = context.getStringAttribute("databaseId");
if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {
return;
}
Integer fetchSize = context.getIntAttribute("fetchSize");
Integer timeout = context.getIntAttribute("timeout");
String parameterMap = context.getStringAttribute("parameterMap");
String parameterType = context.getStringAttribute("parameterType");
Class<?> parameterTypeClass = resolveClass(parameterType);
String resultMap = context.getStringAttribute("resultMap");
String resultType = context.getStringAttribute("resultType");
String lang = context.getStringAttribute("lang");
LanguageDriver langDriver = getLanguageDriver(lang);
Class<?> resultTypeClass = resolveClass(resultType);
String resultSetType = context.getStringAttribute("resultSetType");
StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);
String nodeName = context.getNode().getNodeName();
SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
boolean useCache = context.getBooleanAttribute("useCache", isSelect);
boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);
// Include Fragments before parsing
XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
includeParser.applyIncludes(context.getNode());
// Parse selectKey after includes and remove them.
processSelectKeyNodes(id, parameterTypeClass, langDriver);
// Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);
String resultSets = context.getStringAttribute("resultSets");
String keyProperty = context.getStringAttribute("keyProperty");
String keyColumn = context.getStringAttribute("keyColumn");
KeyGenerator keyGenerator;
String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX;
keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true);
if (configuration.hasKeyGenerator(keyStatementId)) {
keyGenerator = configuration.getKeyGenerator(keyStatementId);
} else {
keyGenerator = context.getBooleanAttribute("useGeneratedKeys",
configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType))
? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
}
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}
解析完MyBatis配置文件后，configuration就初始化完成了，然后根据configuration对象来创建SqlSessionFactory，到这里时，MyBatis的初始化的征程已经走完了。
// SqlSessionFactoryBuilder类
public SqlSessionFactory build(Configuration config) {
return new DefaultSqlSessionFactory(config);
}
从debug调试看出 返回的 sqlSessionFactory 是DefaultSesssionFactory类型的，但是configuration此时已经被初始化了。查看源码后画如下创建DefaultSessionFactory的时序图：
2.2 创建SqlSession的过程
从debug调试看出SqlSessinoFactory.openSession() 返回的sqlSession是DefaultSession类型的，此SqlSession里包含一个Configuration的对象，和一个Executor对象。查看源码后画如下创建DefaultSession的时序图：
2.3 创建Mapper的过程
从debug调试可以看出，mapper是一个Mapper代理对象，而且初始化了Configuration对象，Executor的对象。查看源码后画如下创建Mapper的时序图：
2.4 执行CRUD过程
2.4.1 以select为例查看各步执行的源码
1.mapper.selectEmployeeList()实现原理其实用的jdk动态代理，调试代码发现：
首先是MapperFactoryBean：
/**
* {@inheritDoc}
*/
@Override
public T getObject() throws Exception {
return getSqlSession().getMapper(this.mapperInterface);
}
SqlSessionDaoSupport：它得到的是SqlSessionTemplate类，它是接口SqlSession的实现类。
public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
if (!this.externalSqlSession) {
this.sqlSession = new SqlSessionTemplate(sqlSessionFactory);
}
}
public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {
this.sqlSession = sqlSessionTemplate;
this.externalSqlSession = true;
}
/**
* Users should use this method to get a SqlSession to call its statement methods
* This is SqlSession is managed by spring. Users should not commit/rollback/close it
* because it will be automatically done.
*
* @return Spring managed thread safe SqlSession
*/
public SqlSession getSqlSession() {
return this.sqlSession;
}
SqlSessionTemplate：
/**
* {@inheritDoc}
*/
@Override
public <T> T getMapper(Class<T> type) {
return getConfiguration().getMapper(type, this);
}
SqlSessionTemplate：
@Override
public Configuration getConfiguration() {
return this.sqlSessionFactory.getConfiguration();
}
DefaultSqlSessionFactory：
@Override
public Configuration getConfiguration() {
return configuration;
}
然后是Configuration:
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
return this.mapperRegistry.getMapper(type, sqlSession);
}
最后是MapperRegistry:
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory)this.knownMappers.get(type);
if(mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
} else {
try {
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception var5) {
throw new BindingException("Error getting mapper instance. Cause: " + var5, var5);
}
}
}
该方法中最关键代码:mapperProxyFactory.newInstance(sqlSession);
MapperProxyFactory是一个创建MapperProxy的工厂类,调用其中的newInstance方法可以获取到一个代理对象,继续往下看
MapperProxyFactory:
protected T newInstance(MapperProxy<T> mapperProxy) {
return Proxy.newProxyInstance(this.mapperInterface.getClassLoader(), new Class[]{this.mapperInterface}, mapperProxy);
}
public T newInstance(SqlSession sqlSession) {
MapperProxy<T> mapperProxy = new MapperProxy(sqlSession, this.mapperInterface, this.methodCache);
return this.newInstance(mapperProxy);
}
在该类中可以看到, Proxy.newProxyInstance(this.mapperInterface.getClassLoader(), new Class[]{this.mapperInterface}, mapperProxy);
最终由JDK的动态代理,动态的为我们在内存中创建了一个代理对象。到此,我们已经看到了一部分真相,就是我们为mybatis提供Mapper接口,而mybatis使用JDK的动态代理为我们生成实现类。
下面就是InvocationHandler的实现,从上面的代码中可以看到,它叫做MapperProxy
MapperProxy:
public class MapperProxy<T> implements InvocationHandler, Serializable {
private static final long serialVersionUID = -6424540398559729838L;
private final SqlSession sqlSession;
private final Class<T> mapperInterface;
private final Map<Method, MapperMethod> methodCache;
public MapperProxy(SqlSession sqlSession, Class<T> mapperInterface, Map<Method, MapperMethod> methodCache) {
this.sqlSession = sqlSession;
this.mapperInterface = mapperInterface;
this.methodCache = methodCache;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if(Object.class.equals(method.getDeclaringClass())) {
return method.invoke(this, args);
} else {
MapperMethod mapperMethod = this.cachedMapperMethod(method);
return mapperMethod.execute(this.sqlSession, args);
}
}
private MapperMethod cachedMapperMethod(Method method) {
MapperMethod mapperMethod = (MapperMethod)this.methodCache.get(method);
if(mapperMethod == null) {
mapperMethod = new MapperMethod(this.mapperInterface, method, this.sqlSession.getConfiguration());
this.methodCache.put(method, mapperMethod);
}
return mapperMethod;
}
}
在invoke方法中可以看到,如果我们调用的是Object中的方法,不做任何处理,直接调用,否则执行:mapperMethod.execute(this.sqlSession, args)。
MapperMethod:经过上面的调用后进入MapperMethod里面执行
//判断sql命令类型
public Object execute(SqlSession sqlSession, Object[] args) {
Object param;
Object result;
if(SqlCommandType.INSERT == this.command.getType()) {
param = this.method.convertArgsToSqlCommandParam(args);
result = this.rowCountResult(sqlSession.insert(this.command.getName(), param));
} else if(SqlCommandType.UPDATE == this.command.getType()) {
param = this.method.convertArgsToSqlCommandParam(args);
result = this.rowCountResult(sqlSession.update(this.command.getName(), param));
} else if(SqlCommandType.DELETE == this.command.getType()) {
param = this.method.convertArgsToSqlCommandParam(args);
result = this.rowCountResult(sqlSession.delete(this.command.getName(), param));
} else if(SqlCommandType.SELECT == this.command.getType()) {
//我们测试的是select类型，则再判断这个方法的返回类型
if(this.method.returnsVoid() && this.method.hasResultHandler()) {
this.executeWithResultHandler(sqlSession, args);
result = null;
} else if(this.method.returnsMany()) {
//我们是查询列表，此方法执行
result = this.executeForMany(sqlSession, args);
} else if(this.method.returnsMap()) {
result = this.executeForMap(sqlSession, args);
} else {
param = this.method.convertArgsToSqlCommandParam(args);
result = sqlSession.selectOne(this.command.getName(), param);
}
} else {
if(SqlCommandType.FLUSH != this.command.getType()) {
throw new BindingException("Unknown execution method for: " + this.command.getName());
} result = sqlSession.flushStatements();
} if(result == null && this.method.getReturnType().isPrimitive() && !this.method.returnsVoid()) {
throw new BindingException("Mapper method '" + this.command.getName() + " attempted to return null from a method with a primitive return type (" + this.method.getReturnType() + ").");
} else {
return result;
}
} private <E> Object executeForMany(SqlSession sqlSession, Object[] args) {
//将param做处理 自动处理为param1,param2..
Object param = this.method.convertArgsToSqlCommandParam(args);
List result;
if(this.method.hasRowBounds()) {
RowBounds rowBounds = this.method.extractRowBounds(args);
//调用该对象的DefaultSqlSession的selectList方法
result = sqlSession.selectList(this.command.getName(), param, rowBounds);
} else {
result = sqlSession.selectList(this.command.getName(), param);
} return !this.method.getReturnType().isAssignableFrom(result.getClass())?(this.method.getReturnType().isArray()?this.convertToArray(result):this.convertToDeclaredCollection(sqlSession.getConfiguration(), result)):result;
} //处理参数方法
public Object convertArgsToSqlCommandParam(Object[] args) {
int paramCount = this.params.size();
if(args != null && paramCount != 0) {
if(!this.hasNamedParameters && paramCount == 1) {
return args[((Integer)this.params.keySet().iterator().next()).intValue()];
} else {
Map<String, Object> param = new MapperMethod.ParamMap();
int i = 0; for(Iterator i$ = this.params.entrySet().iterator(); i$.hasNext(); ++i) {
Entry<Integer, String> entry = (Entry)i$.next();
param.put(entry.getValue(), args[((Integer)entry.getKey()).intValue()]);
String genericParamName = "param" + String.valueOf(i + 1);
if(!param.containsKey(genericParamName)) {
param.put(genericParamName, args[((Integer)entry.getKey()).intValue()]);
}
} return param;
}
} else {
return null;
}
}
主要将SQL分为两类执行,DML和SQL。如果是DML,调用SQLSession中对应的方法执行,并且使用rowCountResult方法根据方法的返回值和受影响的行数做处理。
如果是查询,则要根据方法的返回值的类型来执行不同的方法。如果Collection系的集合获取数组来接收,使用selectList方法执行查询。如果使用Map集合,调用selectMap方法执行查询。否则,调用selectOne执行查询。
下面是调用DefaultSqlSession的selectList的方法
public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
List var5;
try {
//获取MappedStatement对象
MappedStatement ms = this.configuration.getMappedStatement(statement);
//调用cachingExecutor执行器的方法
var5 = this.executor.query(ms, this.wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
} catch (Exception var9) {
throw ExceptionFactory.wrapException("Error querying database. Cause: " + var9, var9);
} finally {
ErrorContext.instance().reset();
}
return var5;
}
//CachingExector的query方法
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
//
BoundSql boundSql = ms.getBoundSql(parameterObject);
CacheKey key = this.createCacheKey(ms, parameterObject, rowBounds, boundSql);
//调用下2代码
return this.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
//2代码
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
Cache cache = ms.getCache();
if(cache != null) {
this.flushCacheIfRequired(ms);
if(ms.isUseCache() && resultHandler == null) {
this.ensureNoOutParams(ms, parameterObject, boundSql);
List<E> list = (List)this.tcm.getObject(cache, key);
if(list == null) {
//这里是调用Executor里的query方法 如果开启了缓存这掉CachingExecutor的 如果没有则是调用BaseExecutor的
list = this.delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
this.tcm.putObject(cache, key, list);
}
return list;
}
}
return this.delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
BaseExecutor的query方法
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
if(this.closed) {
throw new ExecutorException("Executor was closed.");
} else {
if(this.queryStack == 0 && ms.isFlushCacheRequired()) {
this.clearLocalCache();
}
List list;
try {
++this.queryStack;
list = resultHandler == null?(List)this.localCache.getObject(key):null;
if(list != null) {
this.handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
} else {
//如果缓存中没有就从数据库中查询
list = this.queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
}
} finally {
--this.queryStack;
}
if(this.queryStack == 0) {
Iterator i$ = this.deferredLoads.iterator();
while(i$.hasNext()) {
BaseExecutor.DeferredLoad deferredLoad = (BaseExecutor.DeferredLoad)i$.next();
deferredLoad.load();
}
this.deferredLoads.clear();
if(this.configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
this.clearLocalCache();
}
}
return list;
}
}
//从数据库中查询
private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
//放入缓存
this.localCache.putObject(key, ExecutionPlaceholder.EXECUTION_PLACEHOLDER);
List list;
try {
//此处是调用子Executor的方法，ExecutorType默认是使用的SimpleExecutor
list = this.doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
} finally {
this.localCache.removeObject(key);
}
this.localCache.putObject(key, list);
if(ms.getStatementType() == StatementType.CALLABLE) {
this.localOutputParameterCache.putObject(key, parameter);
}
return list;
}
SimpleExecutor的doQuery方法
public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
Statement stmt = null;
List var9;
try {
Configuration configuration = ms.getConfiguration();
//创建StateMentHandler处理器
StatementHandler handler = configuration.newStatementHandler(this.wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
//调用下3的方法
stmt = this.prepareStatement(handler, ms.getStatementLog());
//调用no4的方法
var9 = handler.query(stmt, resultHandler);
} finally {
this.closeStatement(stmt);
}
return var9;
}
//下3方法
private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
Connection connection = this.getConnection(statementLog);
Statement stmt = handler.prepare(connection);
//SatementHanlder 采用PreparedStatementHandler来实现此方法，而PreparedStatementHandler调用的是父接口ParameterHandler的方法
handler.parameterize(stmt);
return stmt;
}
ParameterHandler参数处理器的方法
public interface ParameterHandler {
Object getParameterObject();
//此方法是用DefaultParameterHandler实现的
void setParameters(PreparedStatement var1) throws SQLException;
}
DefaultParameterHandler默认参数处理器的方法
public void setParameters(PreparedStatement ps) {
ErrorContext.instance().activity("setting parameters").object(this.mappedStatement.getParameterMap().getId());
List<ParameterMapping> parameterMappings = this.boundSql.getParameterMappings();
if(parameterMappings != null) {
for(int i = 0; i < parameterMappings.size(); ++i) {
ParameterMapping parameterMapping = (ParameterMapping)parameterMappings.get(i);
if(parameterMapping.getMode() != ParameterMode.OUT) {
String propertyName = parameterMapping.getProperty();
Object value;
if(this.boundSql.hasAdditionalParameter(propertyName)) {
value = this.boundSql.getAdditionalParameter(propertyName);
} else if(this.parameterObject == null) {
value = null;
} else if(this.typeHandlerRegistry.hasTypeHandler(this.parameterObject.getClass())) {
value = this.parameterObject;
} else {
MetaObject metaObject = this.configuration.newMetaObject(this.parameterObject);
value = metaObject.getValue(propertyName);
}
//这里用调用 TypeHandler类型映射处理器来映射
TypeHandler typeHandler = parameterMapping.getTypeHandler();
JdbcType jdbcType = parameterMapping.getJdbcType();
if(value == null && jdbcType == null) {
jdbcType = this.configuration.getJdbcTypeForNull();
}
try {
//类型处理器设置参数映射
typeHandler.setParameter(ps, i + 1, value, jdbcType);
} catch (TypeException var10) {
throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + var10, var10);
} catch (SQLException var11) {
throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + var11, var11);
}
}
}
}
}
no4的方法
public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
//此处调用原生sql的处理器
PreparedStatement ps = (PreparedStatement)statement;
//发出原生sql命令
ps.execute();
//采用ResultHandler结果处理器对结果集封装
return this.resultSetHandler.handleResultSets(ps);
}
ResultHandler代码
public interface ResultSetHandler {
//此处调用的是DefaultResultSetHandler的方法
<E> List<E> handleResultSets(Statement var1) throws SQLException;
void handleOutputParameters(CallableStatement var1) throws SQLException;
}
DefaultResultSetHandler的方法
public List<Object> handleResultSets(Statement stmt) throws SQLException {
ErrorContext.instance().activity("handling results").object(this.mappedStatement.getId());
List<Object> multipleResults = new ArrayList();
int resultSetCount = 0;
ResultSetWrapper rsw = this.getFirstResultSet(stmt);
List<ResultMap> resultMaps = this.mappedStatement.getResultMaps();
int resultMapCount = resultMaps.size();
this.validateResultMapsCount(rsw, resultMapCount);
while(rsw != null && resultMapCount > resultSetCount) {
ResultMap resultMap = (ResultMap)resultMaps.get(resultSetCount);
this.handleResultSet(rsw, resultMap, multipleResults, (ResultMapping)null);
rsw = this.getNextResultSet(stmt);
this.cleanUpAfterHandlingResultSet();
++resultSetCount;
}
String[] resultSets = this.mappedStatement.getResulSets();
if(resultSets != null) {
while(rsw != null && resultSetCount < resultSets.length) {
ResultMapping parentMapping = (ResultMapping)this.nextResultMaps.get(resultSets[resultSetCount]);
if(parentMapping != null) {
String nestedResultMapId = parentMapping.getNestedResultMapId();
ResultMap resultMap = this.configuration.getResultMap(nestedResultMapId);
this.handleResultSet(rsw, resultMap, (List)null, parentMapping);
}
rsw = this.getNextResultSet(stmt);
this.cleanUpAfterHandlingResultSet();
++resultSetCount;
}
}
return this.collapseSingleResultList(multipleResults);
}
//处理结果集
private void handleResultSet(ResultSetWrapper rsw, ResultMap resultMap, List<Object> multipleResults, ResultMapping parentMapping) throws SQLException {
try {
if(parentMapping != null) {
this.handleRowValues(rsw, resultMap, (ResultHandler)null, RowBounds.DEFAULT, parentMapping);
} else if(this.resultHandler == null) {
DefaultResultHandler defaultResultHandler = new DefaultResultHandler(this.objectFactory);
this.handleRowValues(rsw, resultMap, defaultResultHandler, this.rowBounds, (ResultMapping)null);
multipleResults.add(defaultResultHandler.getResultList());
} else {
this.handleRowValues(rsw, resultMap, this.resultHandler, this.rowBounds, (ResultMapping)null);
}
} finally {
this.closeResultSet(rsw.getResultSet());
}
}
private void handleRowValues(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
if(resultMap.hasNestedResultMaps()) {
this.ensureNoRowBounds();
this.checkResultHandler();
this.handleRowValuesForNestedResultMap(rsw, resultMap, resultHandler, rowBounds, parentMapping);
} else {
this.handleRowValuesForSimpleResultMap(rsw, resultMap, resultHandler, rowBounds, parentMapping);
}
}
private void handleRowValuesForNestedResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
DefaultResultContext<Object> resultContext = new DefaultResultContext();
this.skipRows(rsw.getResultSet(), rowBounds);
Object rowValue = null;
while(this.shouldProcessMoreRows(resultContext, rowBounds) && rsw.getResultSet().next()) {
ResultMap discriminatedResultMap = this.resolveDiscriminatedResultMap(rsw.getResultSet(), resultMap, (String)null);
CacheKey rowKey = this.createRowKey(discriminatedResultMap, rsw, (String)null);
Object partialObject = this.nestedResultObjects.get(rowKey);
if(this.mappedStatement.isResultOrdered()) {
if(partialObject == null && rowValue != null) {
this.nestedResultObjects.clear();
this.storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
}
//获取行的值
rowValue = this.getRowValue(rsw, discriminatedResultMap, rowKey, (String)null, partialObject);
} else {
rowValue = this.getRowValue(rsw, discriminatedResultMap, rowKey, (String)null, partialObject);
if(partialObject == null) {
this.storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
}
}
}
if(rowValue != null && this.mappedStatement.isResultOrdered() && this.shouldProcessMoreRows(resultContext, rowBounds)) {
this.storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
}
}
String resultMapId = resultMap.getId();
Object resultObject = partialObject;
if(partialObject != null) {
MetaObject metaObject = this.configuration.newMetaObject(partialObject);
this.putAncestor(partialObject, resultMapId, columnPrefix);
this.applyNestedResultMappings(rsw, resultMap, metaObject, columnPrefix, combinedKey, false);
this.ancestorObjects.remove(resultMapId);
} else {
ResultLoaderMap lazyLoader = new ResultLoaderMap();
resultObject = this.createResultObject(rsw, resultMap, lazyLoader, columnPrefix);
if(resultObject != null && !this.typeHandlerRegistry.hasTypeHandler(resultMap.getType())) {
MetaObject metaObject = this.configuration.newMetaObject(resultObject);
boolean foundValues = !resultMap.getConstructorResultMappings().isEmpty();
if(this.shouldApplyAutomaticMappings(resultMap, true)) {
foundValues = this.applyAutomaticMappings(rsw, resultMap, metaObject, columnPrefix) || foundValues;
}
foundValues = this.applyPropertyMappings(rsw, resultMap, metaObject, lazyLoader, columnPrefix) || foundValues;
this.putAncestor(resultObject, resultMapId, columnPrefix);
foundValues = this.applyNestedResultMappings(rsw, resultMap, metaObject, columnPrefix, combinedKey, true) || foundValues;
this.ancestorObjects.remove(resultMapId);
foundValues = lazyLoader.size() > 0 || foundValues;
resultObject = foundValues?resultObject:null;
}
if(combinedKey != CacheKey.NULL_CACHE_KEY) {
this.nestedResultObjects.put(combinedKey, resultObject);
}
}
return resultObject;
}
private boolean shouldApplyAutomaticMappings(ResultMap resultMap, boolean isNested) {
return resultMap.getAutoMapping() != null?resultMap.getAutoMapping().booleanValue():(isNested?AutoMappingBehavior.FULL == this.configuration.getAutoMappingBehavior():AutoMappingBehavior.NONE != this.configuration.getAutoMappingBehavior());
}
private boolean applyAutomaticMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, String columnPrefix) throws SQLException {
List<DefaultResultSetHandler.UnMappedColumAutoMapping> autoMapping = this.createAutomaticMappings(rsw, resultMap, metaObject, columnPrefix);
boolean foundValues = false;
if(autoMapping.size() > 0) {
Iterator i$ = autoMapping.iterator();
while(true) {
//这里使用了内部类对参数和结果集进行映射
DefaultResultSetHandler.UnMappedColumAutoMapping mapping;
Object value;
do {
if(!i$.hasNext()) {
return foundValues;
}
mapping = (DefaultResultSetHandler.UnMappedColumAutoMapping)i$.next();
value = mapping.typeHandler.getResult(rsw.getResultSet(), mapping.column);
} while(value == null && !this.configuration.isCallSettersOnNulls());
if(value != null || !mapping.primitive) {
metaObject.setValue(mapping.property, value);
}
foundValues = true;
}
} else {
return foundValues;
}
}
private static class UnMappedColumAutoMapping {
private final String column;
private final String property;
private final TypeHandler<?> typeHandler;
private final boolean primitive;
//此处才类型器对结果进行映射
public UnMappedColumAutoMapping(String column, String property, TypeHandler<?> typeHandler, boolean primitive) {
this.column = column;
this.property = property;
this.typeHandler = typeHandler;
this.primitive = primitive;
}
}
本文转自：https://blog.csdn.net/u014297148/article/details/78696096