MyBatis3 开发环境搭建

1. 准备工作

下载并导入SQL数据文件：测试数据库脚本
下载相关JAR文件
1. MyBatis3核心jar文件：mybatis-3.2.2.jar
2. Mysql数据库驱动文件：mysql-connector-java-5.1.0-bin.jar

2. MyBatis3开发环境搭建

创建 JavaWeb 项目 MyBatisDemo
将相关JAR文件复制到WebRoot/WEB-INF/lib目录下
创建源码目录 resources 和 test

3. 创建配置文件

在 resources 目录下创建 mybatis-config.xml 文件
在 mybatis-config.xml 文件中键入如下代码：

<?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">
<configuration><!-- 配置多套运行环境 default:默认执行的环境 --><environments default="dev"><!-- 配置运行环境 id:配置环境名称，不能重复 --><environment id="dev"><!-- 配置事务管理器 type：事务管理器类型 --><transactionManager type="JDBC"/><!-- 配置数据源 type：数据源类型 --><dataSource type="POOLED"><!-- 设置驱动 --><property name="driver" value="com.mysql.jdbc.Driver"/><!-- 设置连接字符串 --><property name="url" value="jdbc:mysql://127.0.0.1:3306/smbms?useUnicode=true&amp;characterEncoding=utf-8"/><!-- 用户名 --><property name="username" value="root"/><!-- 密码 --><property name="password" value="ok"/></dataSource></environment></environments>
</configuration>

4. 创建XML映射文件

在 src 目录中创建包 dao.user
在 dao.user 包中创建文件 UserMapper.xml
在 UserMapper.xml 中键入如下代码：

<?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">
<mapper namespace="dao.user.UserMapper"><!-- 查询语句 id:唯一标识 resultType:返回值类型 --><select id="getCount" resultType="int">select count(1) as count from smbms_user</select>
</mapper>

在 mybatis-config.xml 中配置 XML映射文件

<mappers><mapper resource="dao/user/UserMapper.xml"/>
</mappers>

5. 使用MyBatis3访问数据库

在 test 目录中创建 单元测试文件 UserTest.java
在 UserTest.java 中键入以下内容:

import java.io.IOException;
import java.io.InputStream;
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 org.junit.Test;
public class UserMapperTest {@Testpublic void test() {int count = 0;SqlSession sqlSession = null;try {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);sqlSession = factory.openSession();count = sqlSession.selectOne("dao.user.UserMapper.getCount");System.out.println(count);} catch (IOException e) {e.printStackTrace();}finally{if (null != sqlSession) {sqlSession.close();}}}
}

MyBatis3 工具封装类

package util;import java.io.IOException;
import java.io.InputStream;import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;/*** MyBatis工具类* @author yacon**/
public class MyBatisUtil {// 声明SqlSessionFactory对象private static SqlSessionFactory factory = null;/*** 创建SqlSessionFactory对象*/static{try {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");factory = new SqlSessionFactoryBuilder().build(is);} catch (IOException e) {e.printStackTrace();}}/*** 创建SqlSession对象* @return*/public static SqlSession createSqlSession(){return factory.openSession(false);}/*** 关闭SqlSession对象* @param sqlSession*/public static void closeSqlSession(SqlSession sqlSession){if(null != sqlSession){sqlSession.close();}}
}

MyBatis3 配置数据源

静态配置

将数据库信息直接写在环境中

<environments default="development"><environment id="development"><transactionManager type="JDBC"></transactionManager><dataSource type="POOLED"><property name="driver" value="com.mysql.jdbc.Driver"/><property name="url" value="jdbc:mysql://127.0.0.1:3306/smbms?useUnicode=true&characterEncoding=utf-8"/><property name="username" value="root"/><property name="password" value="ok"/></dataSource></environment>
</environments>

动态配置

通过指定外部 properties 文件实现

在 resources 目录下创建 database.properties 文件
在 database.properties 文件中键入以下代码：

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/smbms?useUnicode=true&characterEncoding=utf-8
username=root
password=ok

修改 mybatis-config.xml 文件，具体内容如下：

<properties resource="database.properties" />
<environments default="development"><environment id="development"><transactionManager type="JDBC"></transactionManager><dataSource type="POOLED"><property name="driver" value="${driver}" /><property name="url" value="${url}" /><property name="username" value="${username}" /><property name="password" value="${password}" /></dataSource></environment>
</environments>

在properties节点中配置

<properties><property name="driver" value="com.mysql.jdbc.Driver" /><property name="url" value="jdbc:mysql://127.0.0.1:3306/smbms?useUnicode=true&characterEncoding=utf-8" /><property name="username" value="root" /><property name="password" value="ok" />
</properties>
<environments default="development"><environment id="development"><transactionManager type="JDBC"></transactionManager><dataSource type="POOLED"><property name="driver" value="${driver}" /><property name="url" value="${url}" /><property name="username" value="${username}" /><property name="password" value="${password}" /></dataSource></environment>
</environments>

混合模式实现

<properties resource="database.properties"><property name="driver" value="com.mysql.jdbc.Driver" /><property name="url" value="jdbc:mysql://127.0.0.1:3306/smbms?useUnicode=true&characterEncoding=utf-8" /><property name="username" value="root" /><property name="password" value="ok" />
</properties>
<environments default="development"><environment id="development"><transactionManager type="JDBC"></transactionManager><dataSource type="POOLED"><property name="driver" value="${driver}" /><property name="url" value="${url}" /><property name="username" value="${username}" /><property name="password" value="${password}" /></dataSource></environment>
</environments>

MyBatis3 日志实现

准备工作

下载Log4j核心文件： log4j-1.2.17.jar
下载Log4j配置文件：log4j.properties

部署 Log4j

将 log4j-1.2.17.jar 文件拷贝到 WebRoot/WEB-INF/lib 目录下
将 log4j.properties 文件拷贝到 resources 目录下

配置 Log4j
打开mybatis-config.xml配置文件，并添加如下代码：

<settings><setting name="logImpl" value="LOG4J" />
</settings>

MyBatis3 通过接口进行数据库访问

1. 创建接口

在 dao.user 包中，创建 UserMapper.java 接口文件
在 UserMapper.java 文件中键入如下代码：

package dao.user;
public interface UserMapper {public int count();
}

2. 修改单元测试文件

package test.user;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import dao.user.UserMapper;
import utils.MybatisUtil;
public class UserTest {@Testpublic void getCount() {SqlSession session = null;try {session = MybatisUtil.openSession();int count = session.getMapper(UserMapper.class).getCount();System.out.println(count);} finally{MybatisUtil.closeSession(session);}}
}

MyBatis3 映射器的注册

直接注册映射器文件

<mappers><mapper resource="dao/user/UserMapper.xml" /><mapper resource="dao/role/RoleMapper.xml" />
</mappers>

通过包名自动注册

该方法会自动寻找并注册当前包及其子包中的映射器文件

<mappers><package name="dao"/>
</mappers>

MyBatis3 创建POJO类

什么是POJO类

POJO类即为持久化类，是指其实例状态需要被MyBatis持久化到数据库中的类。通常情况下，POJO类的类名与数据表名相同，属性名与字段名相同，但这不是必须的，因为MyBatis的映射机制可以解决POJO类中的属性名与数据表字段名不一致的问题。

创建POJO类

在 src 目录中创建包 pojo
在 pojo 包中创建 User.java 文件
在 User.java 文件中键入如下代码：

package pojo;
import java.util.Date;
public class User {private Integer id;private String userCode;private String userName;private String userPassword;private Integer gender;private Date birthday;private String phone;private String address;private Integer userRole;private Integer createdBy;private Date creationDate;private Integer modifyBy;private Date modifyDate;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getUserCode() {return userCode;}public void setUserCode(String userCode) {this.userCode = userCode;}public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}public String getUserPassword() {return userPassword;}public void setUserPassword(String userPassword) {this.userPassword = userPassword;}public Integer getGender() {return gender;}public void setGender(Integer gender) {this.gender = gender;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}public Integer getUserRole() {return userRole;}public void setUserRole(Integer userRole) {this.userRole = userRole;}public Integer getCreatedBy() {return createdBy;}public void setCreatedBy(Integer createdBy) {this.createdBy = createdBy;}public Date getCreationDate() {return creationDate;}public void setCreationDate(Date creationDate) {this.creationDate = creationDate;}public Integer getModifyBy() {return modifyBy;}public void setModifyBy(Integer modifyBy) {this.modifyBy = modifyBy;}public Date getModifyDate() {return modifyDate;}public void setModifyDate(Date modifyDate) {this.modifyDate = modifyDate;}
}

数据库类型与java类型对照表

数据库类型	java类型
int	Integer
bigint	Integer
varchar	String
date	java.util.Date
datetime	java.util.Date

MyBatis3 向SQL语句传参

传入一个参数

在 dao.user.UserMapper 接口中，新增如下方法：

public int del(int id);

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<delete id="del" parameterType="int">
DELETE FROM smbms.smbms_user
WHERE
id = #{id}
</delete>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void del() {SqlSession session = null;try {session = MybatisUtil.openSession();int res = session.getMapper(UserMapper.class).del(17);if (res > 0) {session.commit();System.out.println("删除成功");} else {session.rollback();System.out.println("删除失败");}} finally {MybatisUtil.closeSession(session);}
}

传入多个参数

POJO对象实现

在 dao.user.UserMapper 接口中，新增如下方法：

public int add(User user);

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<insert id="add" parameterType="pojo.User">INSERT INTO smbms.smbms_user(userCode,userName,userPassword,gender,birthday,phone,address,userRole,createdBy,creationDate,modifyBy,modifyDate)VALUES(#{userCode},#{userName},#{userPassword},#{gender},#{birthday},#{phone},#{address},#{userRole},#{createdBy},#{creationDate},#{modifyBy},#{modifyDate});
</insert>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Testpublic void add() {SqlSession session = null;try {session = MybatisUtil.openSession();User user = new User();user.setUserCode("zhangsan");user.setUserName("张三");user.setUserPassword("123456");user.setGender(1);user.setBirthday(new SimpleDateFormat("yyyy-MM-dd").parse("1988-10-11"));user.setPhone("1895111111");user.setAddress("北京市长安路1号");user.setUserRole(1);user.setCreatedBy(1);user.setCreationDate(new SimpleDateFormat("yyy-MM-dd").parse("2019-4-1"));user.setModifyBy(1);user.setModifyDate(new SimpleDateFormat("yyy-MM-dd").parse("2019-5-1"));int res = session.getMapper(UserMapper.class).add(user);if (res > 0) {session.commit();System.out.println("插入成功");}else{session.rollback();System.out.println("插入失败");}} catch (ParseException e) {e.printStackTrace();} finally {MybatisUtil.closeSession(session);}
}

Map对象实现

在 dao.user.UserMapper 接口中，新增如下方法：

public int login(Map<String, String> map);

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="login" parameterType="Map" resultType="int">SELECTCOUNT(1)FROMsmbms_userWHEREuserCode = #{userCode}AND userPassword = #{userPassword}
</select>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void login() {SqlSession session = null;try {session = MybatisUtil.openSession();Map<String, String> map = new HashMap<String, String>();map.put("userCode", "admin");map.put("userPassword", "1234567");int res = session.getMapper(UserMapper.class).login(map);if(res > 0){System.out.println("登陆成功");}else{System.out.println("登陆失败");}} finally {MybatisUtil.closeSession(session);}
}

注解实现

在 dao.user.UserMapper 接口中，新增如下方法：

public int login2(@Param("userCode")String userCode, @Param("userPassword")String userPassword);

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="login2" resultType="int">SELECTCOUNT(1)FROMsmbms_userWHEREuserCode = #{userCode}AND userPassword = #{userPassword}
</select>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void login2() {SqlSession session = null;try {session = MybatisUtil.openSession();int res = session.getMapper(UserMapper.class).login2("admin","1234567");if(res > 0){System.out.println("登陆成功");}else{System.out.println("登陆失败");}} finally {MybatisUtil.closeSession(session);}
}

MyBatis3 类型别名

给具体的类取别名

<typeAliases><typeAlias type="pojo.User" alias="User"/><typeAlias type="pojo.Role" alias="Role"/>
</typeAliases>

给指定包下的类取别名

<typeAliases><package name="pojo"/>
</typeAliases>

MyBatis3 获取查询结果

单表查询

查询单个值

在 dao.user.UserMapper 接口中，新增如下方法：

public String getUserName(@Param("userCode") String userCode);

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="getUserName" resultType="String">SELECTuserNameFROMsmbms_userWHEREuserCode = #{userCode}
</select>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void getUserName(){SqlSession session = null;try{session = MybatisUtil.openSession();String userName = session.getMapper(UserMapper.class).getUserName("admin");System.out.println(userName);} finally {MybatisUtil.closeSession(session);}
}

查询一行数据

在 dao.user.UserMapper 接口中，新增如下方法：

public User getUserById(@Param("id") int id);

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="getUserById" resultType="pojo.User">SELECT*FROMsmbms_userWHEREid = #{id}
</select>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void getUserById(){SqlSession session = null;try{session = MybatisUtil.openSession();User user = session.getMapper(UserMapper.class).getUserById(1);System.out.println(user.getUserCode());System.out.println(user.getUserName());}finally {MybatisUtil.closeSession(session);}
}

查询多行数据

在 dao.user.UserMapper 接口中，新增如下方法：

public List<User> getList();

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="getList" resultType="pojo.User">SELECT*FROMsmbms_user
</select>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void getList() {SqlSession session = null;try {session = MybatisUtil.openSession();List<User> users = session.getMapper(UserMapper.class).getList();for (User user : users) {System.out.println(user.getUserCode() + ":"+ user.getUserName());}} finally {MybatisUtil.closeSession(session);}
}

模糊查询

在 dao.user.UserMapper 接口中，新增如下方法：

public List<User> getListByName(@Param("userName") String userName);

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="getListByName" resultType="pojo.User">SELECT*FROMsmbms_userWHEREuserName LIKE CONCAT('%',#{userName},'%')
</select>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void getListByName() {SqlSession session = null;try {session = MybatisUtil.openSession();List<User> users = session.getMapper(UserMapper.class).getListByName("孙");for (User user : users) {System.out.println(user.getUserCode() + ":"+ user.getUserName());}} finally {MybatisUtil.closeSession(session);}
}

分页查询

在 dao.user.UserMapper 接口中，新增如下方法：

public List<User> getPage(@Param("currentPageNo")Integer currentPageNo,  @Param("pageSize")Integer pageSize);

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="getPage" resultType="User">SELECT*FROMsmbms_userLIMIT#{currentPageNo},#{pageSize}
</select>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void getPage(){SqlSession session = null;try {session = MybatisUtil.openSession();Integer currentPageNo = 2;Integer pageSize = 2;List<User> users = session.getMapper(UserMapper.class).getPage((currentPageNo - 1) * pageSize, pageSize);for (User user : users) {System.out.println(user.getUserCode() + ":" + user.getUserName());}} finally {MybatisUtil.closeSession(session);}
}

多表联合查询

主表引用附表字段

在 pojo.User 类中，新增如下属性和方法：

private String roleName;
public String getRoleName() {return roleName;
}
public void setRoleName(String roleName) {this.roleName = roleName;
}

在 dao.user.UserMapper 接口中，新增如下方法：

public List<User> getListJoinRole();

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="getListJoinRole" resultType="pojo.User">SELECTu.userCode,u.userName,r.roleNameFROMsmbms_user u,smbms_role rWHEREu.userRole = r.id
</select>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void getListJoinRole() {SqlSession session = null;try {session = MybatisUtil.openSession();List<User> users = session.getMapper(UserMapper.class).getListJoinRole();for (User user : users) {System.out.println(user.getUserCode() + ":"+ user.getUserName() + ":" + user.getRoleName());}} finally {MybatisUtil.closeSession(session);}
}

主表引用附表POJO对象

在 pojo 包中创建 role 表的映射类 Role

package pojo;
import java.util.Date;
public class Role {private Integer id;private String roleCode;private String roleName;private Integer createdBy;private Date createDate;private Integer modifyBy;private Date modifyDate;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getRoleCode() {return roleCode;}public void setRoleCode(String roleCode) {this.roleCode = roleCode;}public String getRoleName() {return roleName;}public void setRoleName(String roleName) {this.roleName = roleName;}public Integer getCreatedBy() {return createdBy;}public void setCreatedBy(Integer createdBy) {this.createdBy = createdBy;}public Date getCreateDate() {return createDate;}public void setCreateDate(Date createDate) {this.createDate = createDate;}public Integer getModifyBy() {return modifyBy;}public void setModifyBy(Integer modifyBy) {this.modifyBy = modifyBy;}public Date getModifyDate() {return modifyDate;}public void setModifyDate(Date modifyDate) {this.modifyDate = modifyDate;}
}

在 pojo.User 类中，新增如下属性和方法：

private Role role;
public Role getRole() {return role;
}
public void setRole(Role role) {this.role = role;
}

在 dao.user.UserMapper 接口中，新增如下方法：

public List<User> getListJoinRole();

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="getListJoinRole" resultMap="getListJoinRoleResultMap">SELECTu.userCode,u.userName,r.roleNameFROMsmbms_user u,smbms_role rWHEREu.userRole = r.id
</select>
<resultMap type="pojo.User" id="getListJoinRoleResultMap"><result column="userCode" property="userCode" /><result column="userName" property="userName" /><association property="role" javaType="pojo.Role"><result column="roleName" property="roleName" /></association>
</resultMap>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void getListJoinRole() {SqlSession session = null;try {session = MybatisUtil.openSession();List<User> users = session.getMapper(UserMapper.class).getListJoinRole();for (User user : users) {System.out.println(user.getUserCode() + ":"+ user.getUserName() + ":" + user.getRoleName());}} finally {MybatisUtil.closeSession(session);}
}

主表引用附表POJO对象集合

在 pojo 包中创建 address 表的映射类 Address

package pojo;
import java.util.Date;
public class Address {private Integer id;private String contact;private String addressDesc;private String postCode;private String tel;private Integer createdBy;private Date createdDate;private Integer modifyBy;private Date modifyDate;private Integer userId;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getContact() {return contact;}public void setContact(String contact) {this.contact = contact;}public String getAddressDesc() {return addressDesc;}public void setAddressDesc(String addressDesc) {this.addressDesc = addressDesc;}public String getPostCode() {return postCode;}public void setPostCode(String postCode) {this.postCode = postCode;}public String getTel() {return tel;}public void setTel(String tel) {this.tel = tel;}public Integer getCreatedBy() {return createdBy;}public void setCreatedBy(Integer createdBy) {this.createdBy = createdBy;}public Date getCreatedDate() {return createdDate;}public void setCreatedDate(Date createdDate) {this.createdDate = createdDate;}public Integer getModifyBy() {return modifyBy;}public void setModifyBy(Integer modifyBy) {this.modifyBy = modifyBy;}public Date getModifyDate() {return modifyDate;}public void setModifyDate(Date modifyDate) {this.modifyDate = modifyDate;}public Integer getUserId() {return userId;}public void setUserId(Integer userId) {this.userId = userId;}
}

在 pojo.User 类中，新增如下属性和方法：

private List<Address> addresses;
public List<Address> getAddresses() {return addresses;
}
public void setAddresses(List<Address> addresses) {this.addresses = addresses;
}

在 dao.user.UserMapper 接口中，新增如下方法：

public User getUserAddress(@Param("id") int id);

在 dao.user.UserMapper.xml 映射文件中添加如下代码：

<select id="getUserAddress" resultMap="getUserAddressMap">SELECTa.contact, a.addressDesc, u.userNameFROMsmbms_address a, smbms_user uWHEREa.userId = u.id ANDuserId = 1
</select>
<resultMap type="pojo.User" id="getUserAddressMap"><result column="userName" property="userName"/><collection property="addresses" ofType="pojo.Address"><result column="contact" property="contact"/><result column="addressDesc" property="addressDesc"/></collection>
</resultMap>

在单元测试文件 test.user.UserTest 类中添加如下方法：

@Test
public void getUserAddress() {SqlSession session = null;try {session = MybatisUtil.openSession();User user = session.getMapper(UserMapper.class).getUserAddress(1);System.out.println(user.getUserName());for (Address address : user.getAddresses()) {System.out.println(address.getContact() + ":" + address.getAddressDesc());}} finally {MybatisUtil.closeSession(session);}
}

MyBatis3 结果集映射机制

POJO类属性名与数据表字段名不一致的情况

在 pojo 包下创建类 pojo.Role2，并键入如下代码：

package pojo;
import java.util.Date;
public class Role2 {private Integer id;private String roleCode;private String name; // 表字段 roleNameprivate Integer createdBy;private Date creationDate;private Integer modifyBy;private Date modifyDate;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getRoleCode() {return roleCode;}public void setRoleCode(String roleCode) {this.roleCode = roleCode;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Integer getCreatedBy() {return createdBy;}public void setCreatedBy(Integer createdBy) {this.createdBy = createdBy;}public Date getCreationDate() {return creationDate;}public void setCreationDate(Date creationDate) {this.creationDate = creationDate;}public Integer getModifyBy() {return modifyBy;}public void setModifyBy(Integer modifyBy) {this.modifyBy = modifyBy;}public Date getModifyDate() {return modifyDate;}public void setModifyDate(Date modifyDate) {this.modifyDate = modifyDate;}
}

在 src 目录下创建包 dao.role
在包 dao.role 下创建 RoleMapper.java 接口，并键入如下代码：

package dao.role;
import java.util.List;
import pojo.Role2;
public interface RoleMapper {public List<Role2> getRoleList();
}

在包 dao.role 下创建 RoleMapper.xml 映射文件，并键入如下代码：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="dao.role.RoleMapper"><select id="getRole" resultMap="getRoleMap">SELECT * FROM smbms_role</select><resultMap type="pojo.Role2" id="getRoleMap"><result property="id" column="id" /><result property="roleCode" column="roleCode" /><result property="name" column="roleName" /><result property="createdBy" column="createdBy" /><result property="creationDate" column="creationDate" /><result property="modifyBy" column="modifyBy" /><result property="modifyDate" column="modifyDate" /></resultMap>
</mapper>

在 test 目录下创建包 test.role
在 test.role 目录下创建单元测试类 RoleTest.java，并键入如下代码：

package smbms.role.test;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import pojo.Role2;
import dao.role.RoleMapper;
import utils.MybatisUtil;
public class RoleTest {@Testpublic void getRoleListTest() {SqlSession session = null;try {session = MybatisUtil.openSession();List<Role2> roleList = session.getMapper(RoleMapper.class).getRoleList();for (Role2 role2 : roleList) {}} finally {MybatisUtil.closeSession(session);}}
}

自动映射行为

当字段名和属性名部分相同时，可以通过 autoMappingBehavior 配置项类指定是否需要自动映射

取消自动映射

NONE 表示取消自动映射

<settings><setting name="autoMappingBehavior" value="NONE"/>
</settings>

完全自动映射

FULL 会自动映射任意复杂的结果集（无论是否嵌套）

<settings><setting name="autoMappingBehavior" value="FULL"/>
</settings>

部分自动映射

PARTIAL 只会自动映射没有定义嵌套结果集映射的结果集

<settings><setting name="autoMappingBehavior" value="PARTIAL"/>
</settings>

MyBatis3 动态SQL映射

if

接口

public List<User> getUserList(@Param("rid")Integer rid);

映射

<select id="getUserList" resultType="user">SELECT * FROM smbms_user<if test="rid != null">WHERE userRole=#{rid}</if>
</select>

测试

List<User> users = session.getMapper(UserMapper.class).getUserList(2);
List<User> users = session.getMapper(UserMapper.class).getUserList(null);

where-if / trim-if

接口

public List<User> getUserList(@Param("rid")Integer rid, @Param("name")String name);

映射

<select id="getUserList" resultType="User">SELECT * FROM smbms_user<where><if test="name != null and name != ''">AND userName LIKE CONCAT('%',#{name},'%')</if><if test="rid != null">AND userRole = #{rid}</if></where>
</select>
<!-- 或 -->
<select id="getUserList" resultType="User">SELECT * FROM smbms_user<trim prefix="where" prefixOverrides="and|or"><if test="name != null and name != ''">AND userName LIKE CONCAT('%',#{name},'%')</if><if test="rid != null">AND userRole = #{rid}</if></trim>
</select>

测试

List<User> users1 = sqlSession.getMapper(UserMapper.class).getUserList(null, null);
List<User> users2 = sqlSession.getMapper(UserMapper.class).getUserList(null, 3);
List<User> users3 = sqlSession.getMapper(UserMapper.class).getUserList("孙", null);
List<User> users4 = sqlSession.getMapper(UserMapper.class).getUserList("孙", 3);

foreach

接口

public List<User> getUserListInId(@Param("rids")Integer[] rids);

映射

<select id="getUserListInId" resultType="pojo.User">SELECT * FROM smbms_user WHERE id in<foreach collection="rids" item="rid" open="(" separator="," close=")">#{rid}</foreach>
</select>

测试

Integer[] rids = {1,3,5};
List<User> users = sqlSession.getMapper(UserMapper.class).getUserListInId(rids);

choose-when-otherwise

接口

public List<User> getUserList(@Param("rid")Integer rid, @Param("name")String name);

映射

<select id="getUserList" resultType="user">SELECT * FROM smbms_user<choose><when test="rid != null">WHERE userRole = #{rid}</when><when test="name != null">WHERE userName LIKE CONCAT('%',#{name}, '%')</when></choose>
</select>

测试

session.getMapper(UserMapper.class).getUserList(2,"孙");
session.getMapper(UserMapper.class).getUserList(null,"孙");

set-if / trim-if

接口

public Integer setUser(User user);

映射

<update id="setUser">UPDATE smbms.smbms_user<set><if test="userCode != null">userCode = #{userCode} , </if><if test="userName != null">userName = #{userName}, </if><if test="userPassword != null">userPassword = #{userPassword} ,</if><if test="gender != null">gender = #{gender} , </if><if test="birthday != null">birthday = #{birthday} , </if><if test="phone != null">phone = #{phone} , </if><if test="address != null">address = #{address} , </if><if test="userRole != null">userRole = #{userRole} ,</if><if test="createdBy != null">createdBy = #{createdBy} , </if><if test="creationDate != null">creationDate = #{creationDate} , </if><if test="modifyBy != null">modifyBy = #{modifyBy} , </if><if test="modifyDate != null">modifyDate = #{modifyDate} , </if></set>WHERE id = #{id}
</update>
<!-- 或 -->
<update id="saveUser">UPDATE smbms_user<trim prefix="set" suffixOverrides="," suffix="WHERE id=#{id}"><if test="userCode != null">userCode = #{userCode} , </if><if test="userName != null">userName = #{userName}, </if><if test="userPassword != null">userPassword = #{userPassword} ,</if><if test="gender != null">gender = #{gender} , </if><if test="birthday != null">birthday = #{birthday} , </if><if test="phone != null">phone = #{phone} , </if><if test="address != null">address = #{address} , </if><if test="userRole != null">userRole = #{userRole} ,</if><if test="createdBy != null">createdBy = #{createdBy} , </if><if test="creationDate != null">creationDate = #{creationDate} , </if><if test="modifyBy != null">modifyBy = #{modifyBy} , </if><if test="modifyDate != null">modifyDate = #{modifyDate} , </if></trim>
</update>

测试

User user = new User();
user.setId(1);
user.setUserCode("admin1");
user.setUserName("管理员");
session.getMapper(UserMapper.class).setUser(user);