MyBatis中多表查询--- 多对多查询操作----角色到用户
作者：互联网
数据库表
中间表
外键
在IDEA中创建maven项目
整体架构
pom.xml
<?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>
<groupId>com.uek</groupId>
<artifactId>mybatis03-study03-moretableQuery-manyTomany</artifactId>
<version>1.0-SNAPSHOT</version>
<!--打包方式-->
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.5</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.12</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.10</version>
</dependency>
</dependencies>
</project>
MyBatis的主配置文件
在resource目录下------SqlMapConfig.xml
<?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>
<!--使用typeAliases配置别名，它只能配置到domian中类的别名-->
<typeAliases>
<package name="com.uek.domian"/>
</typeAliases>
<!--配置环境-->
<environments default="mysql">
<!--配置mysql的环境-->
<environment id="mysql">
<!--配置事务-->
<transactionManager type="JDBC"></transactionManager>
<!--配置连接池-->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf-8&useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<!--配置映射文件的位置-->
<mappers>
<package name="com.uek.dao"/>
</mappers>
</configuration>
实体类
public class Role implements Serializable {
private Integer roleId;
private String roleName;
private String roleDesc;
//多对多映射：一个角色可以赋予多个用户
private List<User> users;
public List<User> getUsers() {
return users;
}
public void setUsers(List<User> users) {
this.users = users;
}
public Integer getRoleId() {
return roleId;
}
public void setRoleId(Integer roleId) {
this.roleId = roleId;
}
public String getRoleName() {
return roleName;
}
public void setRoleName(String roleName) {
this.roleName = roleName;
}
public String getRoleDesc() {
return roleDesc;
}
public void setRoleDesc(String roleDesc) {
this.roleDesc = roleDesc;
}
@Override
public String toString() {
return "Role{" +
"roleId=" + roleId +
", roleName='" + roleName + '\'' +
", roleDesc='" + roleDesc + '\'' +
'}';
}
}
public class User implements Serializable {
private Integer id;
private String username;
private String address;
private String sex;
private Date birthday;
public String getUsername() {
return username;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername(String mybatis_saveuser) {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", address='" + address + '\'' +
", sex='" + sex + '\'' +
", birthday=" + birthday +
'}';
}
}
dao层接口
public interface IRoleDao {
//查询所有角色
List<Role> findAll();
//查询所有的角色，同时获取角色所赋予的用户
//角色到用户
List<Role> findRoleAll();
}
接口配置 IUserDao.xml
注意：在resource目录下新建包时一级一级的建立
必须和dao层的接口的包名一致
<?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">
<mapper namespace="com.uek.dao.IRoleDao">
<!--定义role表的resultMap-->
<resultMap id="roleMap" type="role">
<id property="roleId" column="rid"></id>
<result property="roleName" column="role_name"></result>
<result property="roleDesc" column="role_desc"></result>
<collection property="users" ofType="user">
<id column="id" property="id" ></id>
<result column="username" property="username" ></result>
<result column="address" property="address" ></result>
<result column="sex" property="sex" ></result>
<result column="birthday" property="birthday" ></result>
</collection>
</resultMap>
<!--查询所有-->
<select id="findAll" resultMap="roleMap">
select * from role
</select>
<!--查询所有的角色，同时获取角色所赋予的用户
角色到用户
-->
<select id="findRoleAll" resultMap="roleMap">
select u.*,r.id as rid,r.role_name,r.role_desc from role r left outer join user_role ur on r.id = ur.rid left outer join user u on u.id = ur.uid
</select>
</mapper>
测试类
public class RowTest {
private InputStream in;
private SqlSession sqlSession;
private IRoleDao roleDao;
@Before //用于在测试方法执行之前执行
public void init() throws Exception {
//1.读取配置文件，生成字节输入流
in = Resources.getResourceAsStream("SqlMapConfig.xml");
//2.获取SqlSession对象
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
//3.获取SqlSession对象
sqlSession = factory.openSession();
//4.获取dao的代理对象
roleDao = sqlSession.getMapper(IRoleDao.class);
}
@After //用于在测试方法执行之后执行
public void destroy() throws Exception {
//提交事务
sqlSession.commit();
//6.释放资源
sqlSession.close();
in.close();
}
//查询所有
@Test
public void testFindAll(){
List<Role> roles = roleDao.findAll();
for (Role role : roles) {
System.out.println("--------每个角色的信息--------");
System.out.println(role);
}
}
//查询所有的角色，同时获取角色所赋予的用户
//角色到用户
@Test
public void testFindRlowAll(){
List<Role> ro =roleDao.findRoleAll();
for (Role rol : ro) {
System.out.println(rol);
System.out.println(rol.getUsers());
}
}
}
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标签：return,String,void,private,查询,id,MyBatis,中多表,public 来源： https://blog.csdn.net/weixin_45430616/article/details/104064964