Mybatis简介
什么vb.net教程是 MyBatis?
MyBatis 是一款优秀c#教程的持久层框架,它支持自定义 SQL、存储过程以及高级映射。MyBatis 免除了几乎所有的 JDBC 代码以及设置python基础教程参数和获取结果集的工作。MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO(Plain Old Java Objects,普通老式 Java 对象)为数据库中的记录。
- MyBatis 是一款优秀的持久层框架
- 它支持自定义 SQL、存储过程java基础教程以及高级映射。
- MyBatis 免除了几乎所有的 JDBC 代码以及设置参数和获取结果集的工作。
- MyBatis 可以通过简单的 XML 或注解来配置和映射原始类型、接口和 Java POJO(Plain Old Java Objects,普通老式 Java 对象)为数据库中的记录。
- MyBatis 本是apache的一个开源项目iBatis, 2010年这个项目由apache software foundation 迁移到了google code,并且改名为MyBatis 。2013年11月迁移到Github。
如何获得Mybatis
- maven仓库
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.7</version>
</dependency>
- 中文文档:https://mybatis.org/mybatis-3/zh/index.html
- Github:https://github.com/mybatis/mybatis-3/releases
持久化
持久层
为什么需要Mybatis
第一个Mybatis程序
学习新东西方法:搭建环境-》导入mybatis-》编写代码-》测试
搭建sql教程环境
建库建表
CREATE DATABASE `mybatis`CHARACTER SET utf8 COLLATE utf8_general_ci;
USE `mybatis`;
CREATE TABLE `mybatis`.`user` ( `id` INT(20) NOT NULL COMMENT '主键', `name` VARCHAR(100) NOT NULL COMMENT '用户名', `pwd` VARCHAR(100) NOT NULL COMMENT '密码', PRIMARY KEY (`id`) ) ENGINE=INNODB CHARSET=utf8 COLLATE=utf8_general_ci;
DESCRIBE `mybatis`.`user`;
INSERT INTO `mybatis`.`user` (`id`, `name`, `pwd`) VALUES ('1', 'zhangyq', '123456');
INSERT INTO `mybatis`.`user` (`id`, `name`, `pwd`) VALUES ('2', 'zhangsf', '123456');
INSERT INTO `mybatis`.`user` (`id`, `name`, `pwd`) VALUES ('3', 'zhangdl', '123456');
新建父工程
新建普通maven项目
删除src目录,作为父工程
导入maven依赖
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<!--父工程-->
<groupId>com.qing</groupId>
<artifactId>mybatis-study</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.49</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.7</version>
</dependency>
<!-- https://mvnrepository.com/artifact/junit/junit -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13.2</version>
</dependency>
</dependencies>
</project>
创建第一个子模块
编写mybatis的核心配置文件
官网:https://mybatis.org/mybatis-3/zh/index.html
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--核心配置文件-->
<configuration>
<!--指定默认数据源-->
<environments default="development">
<!--数据源-->
<environment id="development">
<!--事务管理器-->
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
</configuration>
编写mybatis工具类,获取SqlSession
SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句。
package com.qing.utils;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
public class MybatisUtils {
// 构建 SqlSessionFactory 的实例
private static SqlSessionFactory sqlSessionFactory;
static {
try {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 获取 SqlSession
* @return
*/
public static SqlSession getSqlSession() {
return sqlSessionFactory.openSession();
}
}
编写代码测试
实体类
接口
package com.qing.dao;
import com.qing.pojo.User;
import java.util.List;
/**
* 接口
*/
public interface UserMapper {
List<User> getUserList();
}
Mapper
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
<!--id对应接口的方法,返回值类型对应接口返回值,参数类型对应接口方法参数,集合类型写集合泛型类型-->
<select id="getUserList" resultType="com.qing.pojo.User">
select * from mybatis.user
</select>
</mapper>
测试
package com.qing.dao;
import com.qing.pojo.User;
import com.qing.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserMapperTest {
/**
* 方式一:sqlSession.getMapper(UserMapper.class)
*/
@Test
public void test() {
// 获取sqlSession
SqlSession sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = mapper.getUserList();
for (User user : userList) {
System.out.println(user);
}
// 关闭sqlSession
sqlSession.close();
}
}
问题一:Mapper.xml未注册
org.apache.ibatis.binding.BindingException: Type interface com.qing.dao.UserMapper is not known to the MapperRegistry.
at org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:47)
at org.apache.ibatis.session.Configuration.getMapper(Configuration.java:845)
at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:288)
at com.qing.dao.UserMapperTest.test(UserMapperTest.java:20)
解决:mybatis-config.xml中注册Mapper,resource绑定Mapper,必须使用路径/
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--核心配置文件-->
<configuration>
<!--指定默认数据源-->
<environments default="development">
<!--数据源-->
<environment id="development">
<!--事务管理器-->
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/qing/dao/UserMapper.xml"/>
</mappers>
</configuration>
问题二:Mapper文件编译后不存在
java.lang.ExceptionInInitializerError
at com.qing.dao.UserMapperTest.test(UserMapperTest.java:18)
Caused by: org.apache.ibatis.exceptions.PersistenceException:
### Error building SqlSession.
### The error may exist in com/qing/dao/UserMapper.xml
### Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource com/qing/dao/UserMapper.xml
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
解决:pom.xml中配置编译配置
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>mybatis-study</artifactId>
<groupId>com.qing</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>mybatis-01</artifactId>
<!--配置resources,防止资源导出失败问题-->
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
</build>
</project>
问题三:数据库连接SSL错误
org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet successfully received from the server was 2,729 milliseconds ago. The last packet sent successfully to the server was 2,715 milliseconds ago.
### The error may exist in com/qing/dao/UserMapper.xml
### The error may involve com.qing.dao.UserMapper.getUserList
### The error occurred while executing a query
### Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
Caused by: javax.net.ssl.SSLHandshakeException: java.security.cert.CertificateException: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors
Caused by: java.security.cert.CertificateException: java.security.cert.CertPathValidatorException: Path does not chain with any of the trust anchors
解决:mybatis-config.xml中useSSL=true改为useSSL=false
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--核心配置文件-->
<configuration>
<!--指定默认数据源-->
<environments default="development">
<!--数据源-->
<environment id="development">
<!--事务管理器-->
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/qing/dao/UserMapper.xml"/>
</mappers>
</configuration>
测试成功
CRUD
namespace中的包名要和Mapper接口的包名一致
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
<!--id对应接口的方法,返回值类型对应接口返回值,参数类型对应接口方法参数,集合类型写集合泛型类型-->
<select id="getUserList" resultType="com.qing.pojo.User">
select * from mybatis.user
</select>
</mapper>
package com.qing.dao;
import com.qing.pojo.User;
import java.util.List;
/**
* 接口
*/
public interface UserMapper {
/**
* 查询全部用户
* @return
*/
List<User> getUserList();
}
select 选择,查询语句
id 对应接口中的方法名
parameterType 对应接口中方法的请求参数
resultType 对应接口中方法的返回值
集合类型写集合泛型类型
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
<!--查询全部用户-->
<select id="getUserList" resultType="com.qing.pojo.User">
select * from mybatis.user
</select>
<!--id对应接口的方法,返回值类型对应接口返回值,参数类型对应接口方法参数,集合类型写集合泛型类型-->
<!--根据ID查询用户-->
<select id="getUserById" parameterType="int" resultType="com.qing.pojo.User">
select * from mybatis.user where id=#{id}
</select>
</mapper>
package com.qing.dao;
import com.qing.pojo.User;
import java.util.List;
/**
* 接口
*/
public interface UserMapper {
/**
* 查询全部用户
* @return
*/
List<User> getUserList();
/**
* 根据ID查询用户
* @param id
* @return
*/
User getUserById(int id);
}
package com.qing.dao;
import com.qing.pojo.User;
import com.qing.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserMapperTest {
/**
* 查询全部用户
*/
@Test
public void getUserList() {
SqlSession sqlSession = null;
try {
// 获取sqlSession
sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = mapper.getUserList();
for (User user : userList) {
System.out.println(user);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭sqlSession
sqlSession.close();
}
}
/**
* 根据ID查询用户
*/
@Test
public void getUserById() {
SqlSession sqlSession = null;
try {
// 获取sqlSession
sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = mapper.getUserById(1);
System.out.println(user);
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭sqlSession
sqlSession.close();
}
}
}
insert/update/delete 增删改必须提交事务
编写接口
package com.qing.dao;
import com.qing.pojo.User;
import java.util.List;
/**
* 接口
*/
public interface UserMapper {
/**
* 查询全部用户
*
* @return
*/
List<User> getUserList();
/**
* 根据ID查询用户
*
* @param id
* @return
*/
User getUserById(int id);
/**
* 新增用户
*
* @param user
* @return
*/
int insert(User user);
/**
* 修改用户
* @param user
* @return
*/
int update(User user);
/**
* 删除用户
* @param id
* @return
*/
int delete(int id);
}
编写Mapper
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
<!--查询全部用户-->
<select id="getUserList" resultType="com.qing.pojo.User">
select * from mybatis.user
</select>
<!--id对应接口的方法,返回值类型对应接口返回值,参数类型对应接口方法参数,集合类型写集合泛型类型-->
<!--根据ID查询用户-->
<select id="getUserById" parameterType="int" resultType="com.qing.pojo.User">
select * from mybatis.user where id=#{id}
</select>
<!--新增用户-->
<insert id="insert" parameterType="com.qing.pojo.User">
insert into mybatis.user(id,name,pwd) values(#{id},#{name},#{pwd})
</insert>
<!--修改用户-->
<update id="update" parameterType="com.qing.pojo.User">
update mybatis.user set name=#{name},pwd=#{pwd} where id=#{id}
</update>
<!--删除用户-->
<delete id="delete" parameterType="int">
delete from mybatis.user where id=#{id}
</delete>
</mapper>
测试
package com.qing.dao;
import com.qing.pojo.User;
import com.qing.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserMapperTest {
/**
* 查询全部用户
*/
@Test
public void getUserList() {
SqlSession sqlSession = null;
try {
// 获取sqlSession
sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = mapper.getUserList();
for (User user : userList) {
System.out.println(user);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭sqlSession
sqlSession.close();
}
}
/**
* 根据ID查询用户
*/
@Test
public void getUserById() {
SqlSession sqlSession = null;
try {
// 获取sqlSession
sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = mapper.getUserById(1);
System.out.println(user);
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭sqlSession
sqlSession.close();
}
}
/**
* 新增用户
*/
@Test
public void insert() {
SqlSession sqlSession = null;
try {
// 获取sqlSession
sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = new User(4, "张仲景", "123456");
int rows = mapper.insert(user);
System.out.println(rows);
// 提交事务
sqlSession.commit();
System.out.println("提交事务");
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭sqlSession
sqlSession.close();
}
}
/**
* 修改用户
*/
@Test
public void update() {
SqlSession sqlSession = null;
try {
// 获取sqlSession
sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
User user = new User(4, "张仲景二号", "123456");
int rows = mapper.update(user);
System.out.println(rows);
// 提交事务
sqlSession.commit();
System.out.println("提交事务");
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭sqlSession
sqlSession.close();
}
}
/**
* 删除用户
*/
@Test
public void delete() {
SqlSession sqlSession = null;
try {
// 获取sqlSession
sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
int rows = mapper.delete(4);
System.out.println(rows);
// 提交事务
sqlSession.commit();
System.out.println("提交事务");
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭sqlSession
sqlSession.close();
}
}
}
Map的应用
Map传递参数,用key获取即可
对象传递参数,用属性获取即可
只有一个基本类型参数,可以直接获取,可不写parameterType
编写接口
package com.qing.dao;
import com.qing.pojo.User;
import java.util.List;
import java.util.Map;
/**
* 接口
*/
public interface UserMapper {
/**
* 通过Map新增用户
* @param map
* @return
*/
int insertByMap(Map<String,Object> map);
/**
* 通过Map查询用户
* @param map
* @return
*/
List<User> getByMap(Map<String,Object> map);
}
编写Mapper
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--命名空间绑定一个对应的接口-->
<mapper namespace="com.qing.dao.UserMapper">
<!--通过Map新增用户-->
<insert id="insertByMap" parameterType="map">
insert into mybatis.user(id,name,pwd) values(#{userId},#{userName},#{password})
</insert>
<!--通过Map查询用户-->
<select id="getByMap" parameterType="map" resultType="com.qing.pojo.User">
select * from mybatis.user where id=#{userId} and name=#{userName}
</select>
</mapper>
测试
package com.qing.dao;
import com.qing.pojo.User;
import com.qing.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class UserMapperTest {
/**
* 通过Map新增用户
*/
@Test
public void insertByMap() {
SqlSession sqlSession = null;
try {
// 获取sqlSession
sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
Map<String,Object> map = new HashMap<String, Object>();
map.put("userId",4);
map.put("userName","张仲景");
map.put("password","123456");
int rows = mapper.insertByMap(map);
System.out.println(rows);
// 提交事务
sqlSession.commit();
System.out.println("提交事务");
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭sqlSession
sqlSession.close();
}
}
/**
* 通过Map查询用户
*/
@Test
public void getByMap() {
SqlSession sqlSession = null;
try {
// 获取sqlSession
sqlSession = MybatisUtils.getSqlSession();
// 执行SQL
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
Map<String,Object> map = new HashMap<String, Object>();
map.put("userId",4);
map.put("userName","张仲景");
List<User> userList = mapper.getByMap(map);
for (User user : userList) {
System.out.println(user);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// 关闭sqlSession
sqlSession.close();
}
}
}
分类: 100_Mybatis