maybatis--注解查询

maybatis使用注解查询的时候，便不能使用配置查询，否则会报错

单表操作代码示例：

1.主配置文件不变

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--映入数据库配置资源文件-->
    <properties resource="db.properties"/>
    <!--配置驼峰命名法，且settings属性要在文件environments上面-->
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true" />
    </settings>

    <!-- 运行环境配置（整合后归Spring） -->
    <environments default="development">
        <environment id="development">
            <!-- 事物 -->
            <transactionManager type="JDBC" />
            <!-- 连接池 , 可以减少我们获取连接所消耗的时间-->
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 指定映射文件
    如果用注解配置：需要偶配置class的全限定类名-->
    <mappers>
        <!--<mapper resource="com/dao/UserMapper.xml" />-->
        <!--<mapper class="com.dao.UserMapper"></mapper>-->
        <package name="com.dao"></package>
    </mappers>

</configuration>

2.编写实体类

public class User {
    private Integer id;
    private String uname;
    private String pwd;
}

3.DAO层实体类 注解编写

public interface UserMapper {

    @Select("select * from user")
    List<User> findAll();

    @Insert("insert into user(uname,pwd) values(#{uname},#{pwd})")
    int insertUser(User user);

    @Select("select * from user where id=#{id}")
    User find(Integer id);

    @Update("update user set uname=#{uname},pwd=#{pwd} where id=#{id}")
    int updateUser(User user);

    @Delete("delete from user  where id=#{id}")
    int deleteUser(Integer id);

}

4.测试--增删改查

package com;

import com.bean.User;
import com.dao.UserMapper;
import com.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class AnnotationTest01 {
    
    //查询所有
    @Test
    public void m1(){
        SqlSession session = MybatisUtils.getSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        List<User> all = mapper.findAll();
        for (User user : all) {
            System.out.println(user);
        }
        session.commit();
        session.close();
    }
    
    //添加User
    @Test
    public void m2(){
        SqlSession session = MybatisUtils.getSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        User user = new User();
        user.setUname("欧布");
        user.setPwd("asc");
        mapper.insertUser(user);
        session.commit();
        session.close();
    }
    
    //查询单个User
    @Test
    public void m3(){
        SqlSession session = MybatisUtils.getSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        User user = mapper.find(1);
        System.out.println(user);
        session.commit();
        session.close();
    }
    
    //修改User
    @Test
    public void m4(){
        SqlSession session = MybatisUtils.getSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        User user = mapper.find(2);
        user.setPwd("123");
        int i = mapper.updateUser(user);
        session.commit();
        session.close();
    }
    
    //删除User
    @Test
    public void m5(){
        SqlSession session = MybatisUtils.getSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        mapper.deleteUser(2);
        session.commit();
        session.close();
    }
}

一对多查询示例，多的一方

实体类

public class Account {
    private Integer id;
    private String name;
    private Integer money;
    //一对多 多的一方
    private User user;
}

DAO层

public interface AccountMapper {

    @Select("select * from account")
    List<Account> findAll();

    @Select("select * from account")
    @Results(id = "accountMap",value = {
            @Result(id=true,column = "id",property = "id"),
            @Result(column = "name",property = "name"),
            @Result(column = "money",property = "money"),
            @Result(column = "uid",property = "user",
                    one = @One(select = "com.dao.UserMapper.find",fetchType = FetchType.EAGER)
            )//select = "com.dao.UserMapper.find",调用一的一方必须是查询单个find，而不是findAll。
    })
    List<Account> findAllAU();
}

测试

　　//查询所有
    @Test
    public void m1(){
        SqlSession session = MybatisUtils.getSession();
        AccountMapper mapper = session.getMapper(AccountMapper.class);
        //List<Account> all = mapper.findAll();
        List<Account> all = mapper.findAllAU();
        for (Account account : all) {
            System.out.println(account+":"+account.getUser());
        }
        session.commit();
        session.close();
    }