06 mybatis注解开发

mybatis常用注解：

@Insert:实现新增

@Update:实现更新

@Delete:实现删除

@Select:实现查询

@Result:实现结果集封装

@Results:可以与@Result 一起使用，封装多个结果集

@ResultMap:实现引用@Results 定义的封装

@One:实现一对一结果集封装

@Many:实现一对多结果集封装

@SelectProvider: 实现动态 SQL 映射

@CacheNamespace:实现注解二级缓存的使

一、简单crud操作

package cn.itcast.dao;

import cn.itcast.domain.User;

import org.apache.ibatis.annotations.*;

import java.util.List;

public interface UserDao {

/**

* 查询所有用户

* @return

@Select("select * from user")

//@Results相当于配置文件中的<resultMap>

//id = true为主键，不可少

//property是pojo属性名，column查询出的列名称

@Results(id = "userMap", value = {

@Result(id = true, property = "id", column = "id"),

@Result(property = "username",column = "username"),

@Result(property = "address",column = "address"),

@Result(property = "sex",column = "sex"),

@Result(property = "birthday",column = "birthday")

})

public List<User> findAll();

/**

* 根据id查询用户

* @param id

* @return

@Select("select * from user where id = #{id}")

@ResultMap("userMap")

public User findById(Integer id);

/**

* 保存用户

* @param user

@Insert("INSERT INTO USER (username,birthday,sex,address) " +

"VALUES(#{username},#{birthday},#{sex},#{address})")

//如果需要新增成功之后返回主键id，则需要 @SelectKey，

//如果不需要返回主键id则可以不写 @SelectKey

/**

* keyProperty---->pojo属性名

* keyColumn------>查询出的字段名（不一定是表中的字段名）

* resultType----->返回值类型

* before--------->（false）新增之前插入id,(true)新增之后

* statement------>需要执行的查询id语句

@SelectKey(keyProperty = "id",keyColumn = "id",resultType = Integer.class,before = false,

statement = {"select last_insert_id()"})

public void saveUser(User user);

/**

* 修改用户

* @param user

@Update("UPDATE USER SET username=#{username},address=#{address},sex=#{sex},birthday=#{birthday} where id=#{id} ")

public void updateUser(User user);

/**

* 删除用户

* @param userId

* @return

@Delete("delete from user where id = #{uid} ")

public void deleteUser(Integer userId);

/**

* 查询使用聚合函数

* @return

@Select("select count(*) from user ")

int findTotal();

/**

* 模糊查询

* @param name

* @return

@Select("select * from user where username like #{username} ")

List<User> findByName(String name);

}

二、使用注解实现复杂关系映射开发

实现复杂关系映射之前我们可以在映射文件中通过配置<resultMap>来实现，在使用注解开发时我们需要借

助@Results 注解，@Result 注解，@One 注解，@Many 注解。

package cn.itcast.dao;

import cn.itcast.domain.Account;

import cn.itcast.domain.User;

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 java.util.List;

public interface AccountDao {

/**

* 一对一

* 查询所有账户

@Select("select * from account")

@Results(id = "accountMap", value = {

@Result(id = true, property = "id", column = "id"),

@Result(property = "uid", column = "uid"),

@Result(property = "money", column = "money"),

//property ---->pojo属性

//column ---->用户id

//javaType ---->用户.class

//one ---->根据用户id查询用户

@Result(property = "user", column = "uid", javaType = User.class, one = @One(select = "cn.itcast.dao.UserDao.findById"))

})

public List<Account> findAll();

/**

* 根据用户id查询账户

@Select("select * from account where uid = #{uid}")

public List<Account> findByUserId(Integer userId);

}

package cn.itcast.dao;

import cn.itcast.domain.User;

import org.apache.ibatis.annotations.*;

import java.util.List;

public interface UserDao {

/**

* 一对多

* 查询用户信息时，也要查询他的账户列表

* @return

@Select("select * from user")

@Results(id = "userMap",

value = {

@Result(id = true, column = "id", property = "userId"),

@Result(column = "username", property = "userName"),

@Result(column = "sex", property = "userSex"),

@Result(column = "address", property = "userAddress"),

@Result(column = "birthday", property = "userBirthday"),

//property ----->pojo属性

//column ----->用户id

//javaType ----->返回list

//many ---------->根据用户id查询对应的账户

@Result(column = "id", property = "accounts",javaType = List.class,many = @Many(select = "cn.itcast.dao.AccountDao.findByUserId"))

})

public List<User> findAll();

/**

* 根据 id 查询一个用户

* @param userId

* @return

@Select("select * from user where id = #{uid}")

@ResultMap("userMap")

User findById(Integer userId);

}

猜你喜欢