mybatis 一对一，一对多，多对多关系映射查询操作

package com.itheima.domain;

import java.io.Serializable;
import java.util.Date;
import java.util.List;

public class User implements Serializable {
    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    //一对多关系映射，主表实体应该包含从表实体的集合引用
    private List<Account> accounts;

    public List<Account> getAccounts() {
        return accounts;
    }

    public void setAccounts(List<Account> accounts) {
        this.accounts = accounts;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username=‘" + username + ‘\‘‘ +
                ", birthday=" + birthday +
                ", sex=‘" + sex + ‘\‘‘ +
                ", address=‘" + address + ‘\‘‘ +
                ‘}‘;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

package com.itheima.dao;

import com.itheima.domain.QueryVo;
import com.itheima.domain.User;

import java.util.List;

public interface IUserDao {
    /*
    * 查询所有操作
    * */
    List<User> findAll();

    /*
    * 保存一条记录并返回id（直接将id赋给对应的属性）
    * */
    void saveUser(User user);

    /*
    * 更新用户
    * */
    void updateUser(User user);

    /*
    * 删除用户
    * */
    void deleteUser(Integer userId);

    /*
    * 根据Id查询User
    * */
    User findById(Integer userId);

    /*
    * 模糊查询
    * */
    List<User> findByName(String username);

    /*
    * 查询User总数
    * */
    int findTotal();

    /*
    *  根据queryVo查询中的条件查询用户
    * */
    List<User> findByVo(QueryVo vo);

    /*
    * 根据传入参数条件查询
    * @param user 查询的条件：有可能有用户名，有可能有性别，也有可能有地址，可能啥都没有
    * */
    List<User> findUserByCondition(User user);

    /*
    * 根据queryVo中提供的id集合查询用户信息
    * */
    List<User> findUserInIds(QueryVo vo);
}

package com.itheima.domain;

import java.io.Serializable;

public class Account implements Serializable {
    private Integer id;
    private Integer uid;
    private Double money;

    //从表实体应该包含一个主表实体的对像引用
    private User user;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getUid() {
        return uid;
    }

    public void setUid(Integer uid) {
        this.uid = uid;
    }

    public Double getMoney() {
        return money;
    }

    public void setMoney(Double money) {
        this.money = money;
    }

    @Override
    public String toString() {
        return "Account{" +
                "id=" + id +
                ", uid=" + uid +
                ", money=" + money +
                ‘}‘;
    }
}

package com.itheima.dao;

import com.itheima.domain.Account;
import com.itheima.domain.AccountUser;

import java.util.List;

public interface IAccountDao {

    /*
    * 查询所有Account
    * */
    List<Account> findAll();

    /*
    * 查询所有账户，并且带有用户名和地址
    * */
    List<AccountUser> findAllAccountUser();

}