本文将阐述mybatis中的表是一对一关系的情况下如何完成查询操作。
1、环境约束
- win10 64位操作系统
- idea2018.1.5
- jdk-8u162-windows-x64
- mybatis3.2.8
- mysql 6.5
2、前提约束
- 完成idea中创建mybatis项目 https://www.jianshu.com/p/86db0901156f
3、操作步骤
- 创建一个用户表和一个登录表
create table t_user(id int, name varchar(20));
insert into t_user(id,name) values(1,'ali');
insert into t_user(id,name) values(2,'zhangli');
create table t_login(id int, username varchar(20), password varvhar(20), userid int);
insert into t_login(id,username,password,userid) values(1,'aliuser','alipass',1);
insert into t_login(id,username,password,userid) values(2,'zhangliuser','zhanglipass',2);
- 创建两张表对应的实体类
User.java
package net.wanho.entity;
import java.io.Serializable;
public class User implements Serializable {
private int id;
private String name;
public User() {
}
public User(String name)
{
this.name = name;
}
public User(int id, String name) {
this.id = id;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
'}';
}
}
Login.java
package net.wanho.entity;
import java.io.Serializable;
public class Login implements Serializable {
private int id;
private String username;
private String password;
private User user;
public Login(int id, String username, String password) {
this.id = id;
this.username = username;
this.password = password;
}
public Login() {
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "Login{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
- 在UserMapper.java中新增一个查询方法
List selectLogin();
- 在UserMapper.xml中新增标签
- 测试
//关键代码
String resource ="mybatis-config.xml";
Reader reader = Resources.getResourceAsReader(resource);
SqlSessionFactory sqlSessionFactory =new SqlSessionFactoryBuilder().build(reader);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
List loginList = userMapper.selectLogin();
通过单步调试，便能查看到loginList包含t_login以及t_user中的数据。