一、映射文件中的增删改的实现：
1.说明：
- mybatis 允许增删改直接定义以下返回值类型 Ingeger Long Boolean；Integer 和Long 表示增删改成功的数量；Boolean表示增删改成功数量大于0时，返回true，否则返回false；
- 手动提交 openSession.commit();sqlSessionFactory.openSession(); 不会自动提交数据；sqlSessionFactory.openSession(true); 自动提交数据 ,不需要手动提交
2.测试项目目录结构和全局配置文件：
全局配置文件mybatis-config.xml：
配置说明可以参考mybatis全局配置文件说明
1 <?xml version="1.0" encoding="UTF-8" ?>
2 <!DOCTYPE configuration
3 PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
4 "http://mybatis.org/dtd/mybatis-3-config.dtd">
5 <configuration>
6 <properties resource="dbconfig.properties"></properties>
7
8 <environments default="development">
9 <environment id="development">
10 <transactionManager type="JDBC" />
11 <dataSource type="POOLED">
12 <property name="driver" value="${jdbc.driver}" />
13 <property name="url" value="${jdbc.url}" />
14 <property name="username" value="${jdbc.username}" />
15 <property name="password" value="${jdbc.password}" />
16 </dataSource>
17 </environment>
18 <environment id="development_mysql2">
19 <transactionManager type="JDBC" />
20 <dataSource type="POOLED">
21 <property name="driver" value="${jdbc2.driver}" />
22 <property name="url" value="${jdbc2.url}" />
23 <property name="username" value="${jdbc2.username}" />
24 <property name="password" value="${jdbc2.password}" />
25 </dataSource>
26 </environment>
27 </environments>
28
29
30 <mappers>
31 <package name="dao"/>
32 </mappers>
33 </configuration>
View Code
3.添加：
接口EmployeeMapper.java:
1 package dao;
2
3 import entity.Employee;
4
5 public interface EmployeeMapper {
6 void addEmp(Employee employee);
7 }
View Code
映射文件EmployeeMapper.xml;
- parameterType 可以省略
- mybatis支持自增主键，自增主键的获取，mybatis也是利用statement.getGenreatedKeys()
- useGeneratedKeys ="true",使用自增主键获取主键值的策略；
- keyProperty:指定对应的主键属性，也就是mybatis获取到主键以后，将这个值封装给javabean的那个属性
1 <?xml version="1.0" encoding="UTF-8" ?>
2 <!DOCTYPE mapper
3 PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
4 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
5 <mapper namespace="dao.EmployeeMapper">
6 <insert id="addEmp" parameterType="entity.Employee"
7 useGeneratedKeys="true" keyProperty="id">
8 insert into
9 tbl_employee(last_name,gender,email) values(
10 #{lastName},#{gender},#{email}
11 )
12 </insert>
13 </mapper>
View Code
junit 测试类：
1 @Test
2 public void test01() {
3 String resource = "mybatis-config.xml";
4 SqlSession openSession = null;
5 try {
6 InputStream inputStream = Resources.getResourceAsStream(resource);
7 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
8 // 获取openSession 不会自动提交数据
9 openSession = sqlSessionFactory.openSession();
10 EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 Employee employeeAdd = new Employee();
12 employeeAdd.setLastName("joy222");
13 employeeAdd.setGender("女");
14 employeeAdd.setEmail("joy521125@icloud.com");
15 mapper.addEmp(employeeAdd);// 测试新增
16 System.out.println(employeeAdd.getId());
17 openSession.commit();
18 } catch (Exception e) {
19 // TODO: handle exception
20 } finally {
21 if (openSession != null) {
22 openSession.close();
23 }
24
25 }
26 }
oracle中的添加数据的说明：
selectKey标签
- keyProperty:查出的主键键值对封装给javaBean的哪个属性
- order="BEFORE":当前SQL在插入SQL语句前运行；
- resultType：查出数据的返回值类型；
运行顺序：
- 先运行selectKey查询ID的SQL，查出ID值封装给javabean对应的属性
- 再运行插入的SQL语句
1 <insert id="addEmp" databaseId="oracle" parameterType="entity.Employee">
2
3 <selectKey keyProperty="id" order="BEFORE" resultType="Integer">
4 <!-- 编写查询主键的SQL语句 -->
5 select EMPLOYEES_SEQ.NEXTVAL from dual
6 </selectKey>
7 <!-- 插入时的主键是从序列中拿到的 -->
8 insert into tbl_employee(ID,last_name,gender,email) values(
9 #{id},#{lastName},#{gender},#{email}
10 )
11 </insert>
after方式：
先运行插入的SQL（从序列中取出新值作为ID）
再运行selectKey 查询ID的SQL；
<insert id="addEmp" databaseId="oracle" parameterType="entity.Employee">
<selectKey keyProperty="id" order="AFTER" resultType="Integer">
<!-- 编写查询主键的SQL语句 -->
select EMPLOYEES_SEQ.currval from dual
</selectKey>
<!-- 插入时的主键是从序列中拿到的 -->
insert into tbl_employee(ID,last_name,gender,email) values(
EMPLOYEES_SEQ.NEXTVAL,#{lastName},#{gender},#{email}
)
</insert>
4.修改：
接口EmployeeMapper.java:
void updateEmp(Employee employee);
映射文件EmployeeMapper.xml
- parameterType 可以省略
<update id="updateEmp" parameterType="entity.Employee">
update tbl_employee set last_name = #{lastName},gender = #{gender},email=#{email}
where id = #{id}
</update>
junit测试类：
1 public void test01() {
2 String resource = "mybatis-config.xml";
3 SqlSession openSession = null;
4 try {
5 InputStream inputStream = Resources.getResourceAsStream(resource);
6 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
7 // 获取openSession 不会自动提交数据
8 openSession = sqlSessionFactory.openSession();
9 EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
10 Employee employeeAdd2 = new Employee();
11 employeeAdd2.setLastName("joy33333");
12 employeeAdd2.setGender("女");
13 employeeAdd2.setEmail("joy52112225@iclound.com");
14 employeeAdd2.setId(1);
15 mapper.updateEmp(employeeAdd2);// 测试修改
16 // 2.手动提交
17 openSession.commit();
18 } catch (Exception e) {
19 // TODO: handle exception
20 } finally {
21 if (openSession != null) {
22 openSession.close();
23 }
24
25 }
26 }
5.删除：
接口EmployeeMapper.java:
void deleteEmpById(Integer id);
映射文件EmployeeMapper.xml
- parameterType 可以省略
<delete id="deleteEmpById" parameterType="java.lang.Integer">
delete from tbl_employee where id = #{id}
</delete>
junit测试类：
1 @Test
2 public void test01() {
3 String resource = "mybatis-config.xml";
4 SqlSession openSession = null;
5 try {
6 InputStream inputStream = Resources.getResourceAsStream(resource);
7 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
8 // 获取openSession 不会自动提交数据
9 openSession = sqlSessionFactory.openSession();
10 EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 mapper.deleteEmpById(24);// 测试删除
12 // 2.手动提交
13 openSession.commit();
14 } catch (Exception e) {
15 // TODO: handle exception
16 } finally {
17 if (openSession != null) {
18 openSession.close();
19 }
20
21 }
22 }
二、mybatis参数处理：
单个参数：
- mybatis不会做特殊处理，参数名可以随便自定义
- #{参数名}
接口EmployeeMapper.java:
Employee getEmpById(int id);
映射文件EmployeeMapper.xml
- parameterType 可以省略
-
#{id}可以自定义名称，比如#{asdsdfsdf}
<select id="getEmpById" parameterType="Integer" resultType="entity.Employee">
select LAST_NAME AS
lastName,gender as gender,email as email from
tbl_employee where id =#{id}
</select>
junit测试类：
1 @Test
2 public void test03() {
3 String resource = "mybatis-config.xml";
4 SqlSession openSession = null;
5 try {
6 InputStream inputStream = Resources.getResourceAsStream(resource);
7 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
8 // 获取openSession 不会自动提交数据
9 openSession = sqlSessionFactory.openSession(true);
10 EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 // 查询单个参数
12 Employee employee = mapper.getEmpById(1);
13 System.out.println("查询1个参数测试1：" + employee);
14 } catch (Exception e) {
15 // TODO: handle exception
16 } finally {
17 if (openSession != null) {
18 openSession.close();
19 }
20
21 }
22 }
运行结果：
查询1个参数测试1：Employee [id=null, lastName=joy33333, email=joy52112225@iclound.com, gender=女]
多个参数：
1.直接传参：
- 多个参数会被封装成一个map。
- key：param1.。。。paramN
- value：传入的参数值
- #{}就是从map中获取指定的key的值；即#{param1}....#{param10}
映射文件EmployeeMapper.xml：
- parameterType 可以省略
<select id="getEmp" resultType="entity.Employee">
select LAST_NAME AS
lastName,gender as gender,email as email from
tbl_employee where id =#{param1} and last_name = #{param2}
</select>
接口EmployeeMapper.java:
Employee getEmp(int id, String lastName);
junit测试类：
1 @Test
2 public void test04() {
3 String resource = "mybatis-config.xml";
4 SqlSession openSession = null;
5 try {
6 InputStream inputStream = Resources.getResourceAsStream(resource);
7 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
8 // 获取openSession 不会自动提交数据
9 openSession = sqlSessionFactory.openSession(true);
10 EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 // 查询多个参数
12 Employee employee2 = mapper.getEmp(1, "joy33333");
13 System.out.println("查询多个参数测试1：" + employee2);
14 } catch (Exception e) {
15 // TODO: handle exception
16 } finally {
17 if (openSession != null) {
18 openSession.close();
19 }
20
21 }
22 }
运行结果：
查询多个参数测试1：Employee [id=null, lastName=joy33333, email=joy52112225@iclound.com, gender=女]
2.命名参数：明确指定封装参数是map的key@Param("id")
- 多个参数会被封装成一个map
- key:使用@Param("id")注解指定的值
- value:参数值
映射文件EmployeeMapper.xml：
- parameterType 可以省略
<select id="getEmp2" resultType="entity.Employee">
select LAST_NAME AS
lastName,gender as gender,email as email from
tbl_employee where id =#{id} and last_name = #{lastName}
</select>
接口EmployeeMapper.java:
Employee getEmp2(@Param("id") int id, @Param("lastName") String lastName);
junit测试类：
1 @Test
2 public void test04() {
3 String resource = "mybatis-config.xml";
4 SqlSession openSession = null;
5 try {
6 InputStream inputStream = Resources.getResourceAsStream(resource);
7 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
8 // 获取openSession 不会自动提交数据
9 openSession = sqlSessionFactory.openSession(true);
10 EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 // 查询多个参数
12 Employee employee3 = mapper.getEmp2(1, "joy33333");
13 System.out.println("查询多个参数测试2：" + employee3);
14
15 } catch (Exception e) {
16 // TODO: handle exception
17 } finally {
18 if (openSession != null) {
19 openSession.close();
20 }
21
22 }
23 }
运行结果：
查询多个参数测试2：Employee [id=null, lastName=joy33333, email=joy52112225@iclound.com, gender=女]
3.pojo
如果多个参数正好是我们页面逻辑的数据模型，我们就可以直接传入pojo
#{属性名}：取出pojo的属性值
接口EmployeeMapper.java:
Employee getEmp3(Employee emp);
映射文件EmployeeMapper.xml：
- parameterType 可以省略
<select id="getEmp3" resultType="entity.Employee">
select LAST_NAME AS
lastName,gender as gender,email as email from
tbl_employee where id =#{id} and last_name = #{lastName}
</select>
junit 测试类：
1 public void test04() {
2 String resource = "mybatis-config.xml";
3 SqlSession openSession = null;
4 try {
5 InputStream inputStream = Resources.getResourceAsStream(resource);
6 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
7 // 获取openSession 不会自动提交数据
8 openSession = sqlSessionFactory.openSession(true);
9 EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
10 // 查询多个参数
11 Employee employee = new Employee();
12 employee.setId(1);
13 employee.setLastName("joy33333");
14 System.out.println(mapper.getEmp3(employee));
15
16 } catch (Exception e) {
17 // TODO: handle exception
18 } finally {
19 if (openSession != null) {
20 openSession.close();
21 }
22
23 }
24 }
运行结果：
Employee [id=null, lastName=joy33333, email=joy52112225@iclound.com, gender=女]
4.map:
- 如果多个参数不是业务模型中的数据，没有对应的pojo，不经常使用 为了方面，我们也可以传入map
- #{key} 取出map中对应的key
接口EmployeeMapper.java:
Employee getEmpByMap(Map<String, Object> map);
映射文件EmployeeMapper.xml：
- parameterType 可以省略
<select id="getEmpByMap" parameterType="Map" resultType="entity.Employee">
select LAST_NAME AS
lastName,gender as gender,email as email from
tbl_employee where id =#{id} and last_name = #{lastName}
</select>
junit 测试类：
1 @Test
2 public void test04() {
3 String resource = "mybatis-config.xml";
4 SqlSession openSession = null;
5 try {
6 InputStream inputStream = Resources.getResourceAsStream(resource);
7 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
8 // 获取openSession 不会自动提交数据
9 openSession = sqlSessionFactory.openSession(true);
10 EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
11 // 查询多个参数
12 Map<String, Object> map = new HashMap<>();
13 map.put("id", 1);
14 map.put("lastName", "joy33333");
15 Employee employee4 = mapper.getEmpByMap(map);
16 System.out.println("查询多个参数测试3：" + employee4);
17 } catch (Exception e) {
18 // TODO: handle exception
19 } finally {
20 if (openSession != null) {
21 openSession.close();
22 }
23
24 }
25 }
5.TO
如果多个参数不是页面模型中的数据，但是经常要使用，推荐写一个TO(数据传输对象),推荐使用 AO DO TO命名。例如：EmployeeDO；传参方式就是以上的1~4；
6.其他使用场景
Employee getEmp2(@Param("id") int id, String lastName);取值：id==>#{id/param1} lastName==>#{param2}
Employee getEmp2(@Param("id") int id, @Param("e") Employee emp);取值：id==>#{id/param1} lastName==>#{param2.lastName/e.lastName}
7.特别注意
如果是Collection(List Set)类型或者是数组：也会特殊处理。也就是把传入的list或者数组封装在map中
key:Collection(collection) ,如果是List 还可以使用这个key(list)；数组（array）
Employee getEmpById(List<Ingeger> ids);
取值：取出第一个id值：#{list[0]}
三、#{}和${}区别和使用
1.相同点：
#{}:可以获取map中的值获取pojo对象属性的值
${}:可以获取map中的值获取pojo对象属性的值
2.区别：
#{}:以预编译的相识，将参数设置到SQL语句中：PrepaedStatement
${}:取出的值，直接拼装在SQL中，会有安全风险
大多数情况下，使用#{}
原生jdbc不支持占位符的地方就可以使用${}进行取值
比如分表、排序：按照年份拆分
select * from ${year}
select * from tbl_employee order by ${XXX} ${order}
3.#{}:更丰富的用法
a.规定参数的一些规则
javaType jdbcType mode(存储过程) numericScale resultMap typeHandler jdbcTypeName express(为了准备支持的功能) 中需要使用到#{};
b.jdbcType通常需要在某种特定的条件下被设置(经常使用)
在我们数据为null的时候，有些数据可能不能识别mybatis对null的默认处理。比如Oracle（报错 jdbctype other：无效的类型）；因为mybatis对所有的null都映射的是原始jdbc的OTHER,oracle 不能正确处理。
由于全局配置中，jdbcTypeForNull= OTHER oracle不支持，解决办法：
方法1.#{email,jdbcType=NULL} 指定 jdbcType
方法2.jdbcTypeForNull = NULL 即<setting name="jdbcTypeForNull" value="NULL"/>