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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

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

        select l.id, l.username,l.password,u.name from t_login l , t_user  u where l.userid=u.id;        
           
            
            
            
                
                 
             
        
   

• 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。

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