mybatis学习小结(十)

Mybatis中的注解开发
    1.环境搭建以及单表CRUD操作（代理Dao方式）:

      主配置文件:

<?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>
    <!-- 引入外部配置文件-->
    <properties resource="jdbcConfig.properties"></properties>
    <!--配置别名-->
    <typeAliases>
        <package name="com.itheima.domain"></package>
    </typeAliases>
    <!-- 配置环境-->
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"></property>
                <property name="url" value="${jdbc.url}"></property>
                <property name="username" value="${jdbc.username}"></property>
                <property name="password" value="${jdbc.password}"></property>
            </dataSource>
        </environment>
    </environments>
    <!-- 指定带有注解的dao接口所在位置 -->
    <mappers>
        <mapper class="com.itheima.dao.IUserDao"></mapper>
    </mappers>
</configuration>

      带有注解的IUserDao接口:

package com.itheima.dao;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import java.util.List;

/**
 * @author 黑马程序员
 * @Company http://www.ithiema.com
 * 在mybatis中针对,CRUD一共有四个注解
 *  @Select @Insert @Update @Delete
 */
public interface IUserDao {

    /**
     * 查询所有用户
     * @return
     */
    @Select("select * from user")
    List<User> findAll();

    /**
     * 保存用户
     * @param user
     */
    @Insert("insert into user(username,address,sex,birthday)values(#{username},#{address},#{sex},#{birthday})")
    void saveUser(User user);

    /**
     * 更新用户
     * @param user
     */
    @Update("update user set username=#{username},sex=#{sex},birthday=#{birthday},address=#{address} where id=#{id}")
    void updateUser(User user);

    /**
     * 删除用户
     * @param userId
     */
    @Delete("delete from user where id=#{id} ")
    void deleteUser(Integer userId);

    /**
     * 根据id查询用户
     * @param userId
     * @return
     */
    @Select("select * from user  where id=#{id} ")
    User findById(Integer userId);

    /**
     * 根据用户名称模糊查询
     * @param username
     * @return
     */
//    @Select("select * from user where username like #{username} ")
    @Select("select * from user where username like '%${value}%' ")
    List<User> findUserByName(String username);

    /**
     * 查询总用户数量
     * @return
     */
    @Select("select count(*) from user ")
    int findTotalUser();
}

    测试类:

package com.itheima.test;

import com.itheima.dao.IUserDao;
import com.itheima.domain.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

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

/**
 * @author 黑马程序员
 * @Company http://www.ithiema.com
 */
public class AnnotationCRUDTest {
    private InputStream in;
    private SqlSessionFactory factory;
    private SqlSession session;
    private IUserDao userDao;

    @Before
    public  void init()throws Exception{
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        factory = new SqlSessionFactoryBuilder().build(in);
        session = factory.openSession();
        userDao = session.getMapper(IUserDao.class);
    }

    @After
    public  void destroy()throws  Exception{
        session.commit();
        session.close();
        in.close();
    }


    @Test
    public void testSave(){
        User user = new User();
        user.setUsername("mybatis annotation");
        user.setAddress("北京市昌平区");

        userDao.saveUser(user);
    }

    @Test
    public void testUpdate(){
        User user = new User();
        user.setId(53);
        user.setUsername("mybatis annotation update");
        user.setAddress("北京市海淀区");
        user.setSex("男");
        user.setBirthday(new Date());

        userDao.updateUser(user);
    }


    @Test
    public void testDelete(){
        userDao.deleteUser(51);
    }

    @Test
    public void testFindOne(){
        User user = userDao.findById(53);
        System.out.println(user);
    }


    @Test
    public  void testFindByName(){
//        List<User> users = userDao.findUserByName("%mybatis%");
        List<User> users = userDao.findUserByName("mybatis");
        for(User user : users){
            System.out.println(user);
        }
    }

    @Test
    public  void testFindTotal(){
        int total = userDao.findTotalUser();
        System.out.println(total);
    }
}

  mybatis注解建立实体类属性和数据库表中列的对应关系:

    例子:

/**
 * 查询所有用户
 * @return
 */
@Select("select * from user")
@Results(id="userMap",value={  id是提供给其它方法去获取，其他方法上加上@ResultMap(value={"userMap"})即可.
        @Result(id=true,column = "id",property = "userId"),  这个id=true表示表中的id是主键
        @Result(column = "username",property = "userName"),
        @Result(column = "address",property = "userAddress"),
        @Result(column = "sex",property = "userSex"),
        @Result(column = "birthday",property = "userBirthday")    
})

    多表查询操作

    mybatis一对一注解开发的查询配置:

      IAccountDao接口:

package com.itheima.dao;

import com.itheima.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;

/**
 * @author 黑马程序员
 * @Company http://www.ithiema.com
 */
public interface IAccountDao {

    /**
     * 查询所有账户，并且获取每个账户所属的用户信息
     * @return
     */
    @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.itheima.dao.IUserDao.findById",fetchType= FetchType.EAGER))
    })
    List<Account> findAll();

    /**
     * 根据用户id查询账户信息
     * @param userId
     * @return
     */
    @Select("select * from account where uid = #{userId}")
    List<Account> findAccountByUid(Integer userId);
}

     mybatis注解开发一对多的查询配置:

       IUserDao接口:

package com.itheima.dao;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.*;
import org.apache.ibatis.mapping.FetchType;

import java.util.List;

/**
 * @author 黑马程序员
 * @Company http://www.ithiema.com
 * 在mybatis中针对,CRUD一共有四个注解
 *  @Select @Insert @Update @Delete
 */
@CacheNamespace(blocking = true)
public interface IUserDao {

    /**
     * 查询所有用户
     * @return
     */
    @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 = "accounts",column = "id",
                    many = @Many(select = "com.itheima.dao.IAccountDao.findAccountByUid",
                                fetchType = FetchType.LAZY))
    })
    List<User> findAll();

    /**
     * 根据id查询用户
     * @param userId
     * @return
     */
    @Select("select * from user  where id=#{id} ")
    @ResultMap(value={"userMap"})
    User findById(Integer userId);

    /**
     * 根据用户名称模糊查询
     * @param username
     * @return
     */
    @Select("select * from user where username like #{username} ")
    @ResultMap("userMap")
    List<User> findUserByName(String username);


}

    缓存的配置:

     在主配置文件SqlMapConfig.xml中配置

   <!--配置开启二级缓存--> <settings> <setting name="cacheEnabled" value="true"/> </settings>

      不配也行，官方默认为true

    在接口上添加@CacheNamespace(blocking = true)表示开启支持二级缓存

    接着不同的sqlsession对象访问同一条记录的时候（前提是关闭一级缓存）,就会只执行一次查询语句，

    后面的sqlsession对象直接从二级缓存中取