Mybatis关于使用注解问题，参数对应，多表查询

项目结构

1、pojo对象

User对象

package com.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 String address; private String sex; private Date birthday; //一对多 多表查询 private List<Account> accounts; public List<Account> getAccounts() { return accounts; } public void setAccounts(List<Account> accounts) { this.accounts = accounts; } 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 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 + ", accounts=" + accounts + '}'; } }

Account对象

package com.domain; import java.io.Serializable; public class Account implements Serializable { private Integer id; private Integer uid; private Double money; // 多对一 多表查询 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 + ", user=" + user + '}'; } }

2、查询接口

一个User对应多个Account，在UserDao中使用 many UserDao

package com.dao; import com.domain.User; import org.apache.ibatis.annotations.*; import org.apache.ibatis.mapping.FetchType; import java.util.List; public interface UserDao { /*查询所有用户 * 只有主键的值 id 要设置为 true * results的id设置为 userMap，可以方便别语句使用 * 一个用户对应多个账户，在这里使用 many，many中的select中调用的方法在AccountDao中一定要有实现，反之在AccountDao中需要根据账户信息查询用户信息也是一样，具体看实现代码 * @Result(property = "account",column = "id",many=@Many(select="com.dao.AccountDdao.findAccountByUid",fetchType = FetchType.LAZY)) * property:对应User对象中的属性名 * column:user对象的主键ID（因为是要根据user的id去查询account） * many:多表对应 * fetchType:加载时机*/ @Select("select * from user") @Results(id="userMap",value={ @Result(id=true,column="id",property = "userId"), @Result(column = "username",property = "userName"), @Result(column = "address",property = "userAddress"), @Result(column = "sex",property = "userSex"), @Result(column = "birthday",property = "userBirthday"), @Result(property = "account",column = "id",many=@Many(select="com.dao.AccountDdao.findAccountByUid",fetchType = FetchType.LAZY)) }) List<User> findAll(); /*根据id查询用户 在这里可能会出现字段和数据库属性名对应不上，可以通过上面已经编写的 @Results(...)语句来调用 ，@ResultMap(value={"userMap"}) * */ @Select("select * from user where id=#{id}") @ResultMap(value={"userMap"}) User findById(Integer userId); /*保存用户*/ @Insert("insert into user(username,address,sex,birthday) values(#{username),#{address},#{sex},#{birthday}") void saveUser(User user); /*根据用户名模糊查询*/ // 方式一：name在传过来之前，就已经添加了 % 。值为 %xxx% // @Select("select * from user where name like #{name}") // 方式二： @Select("select * from user where user like '%${name}%'") List<User> findUserByName(String username); }

AccountDao 多个Account对应一个User，在AccountDao中使用 one

package com.dao; import com.domain.Account; import org.apache.ibatis.annotations.One; import org.apache.ibatis.annotations.Result; import org.apache.ibatis.annotations.Results; import org.apache.ibatis.annotations.Select; import org.apache.ibatis.mapping.FetchType; import java.util.List; public interface AccountDao { /*查询所有账户，并且获取每个账户所属的用户信息*/ @Select("select * from account") @Results(id="accountMap",value={ @Result(id=true,column="id",property = "id"), @Result(column = "uid",property = "uid"), @Result(column = "money",property = "money"), @Result(property = "user",column="uid",one=@One(select="com.dao.UserDao.findById",fetchType = FetchType.EAGER)) }) List<Account> findAll(); /*根据用户id查询账户信息*/ @Select("select * from account where uid=#{userId}") List<Account> findAccountByUid(Integer userId); }