标签：iat ring family enable lazyload actor 一级缓存 不能 tran
第四天：mybatis的缓存和注解开发
mybatis中的加载时机（查询的时机）
mybatis中的一级缓存和二级缓存
mybatis的注解开发
单表CRUD
多表查询
一、今日内容概要
二、Mybatis中的延迟加载
1.一对一实现延迟加载
IAccountDao.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.itheima.dao.IAccountDao"> <!-- 定义封装account和user的resultMap --> <resultMap id="accountUserMap" type="account"> <id property="id" column="id"></id> <result property="uid" column="uid"></result> <result property="money" column="money"></result> <!-- 一对一的关系映射：配置封装user的内容 select属性指定的内容：查询用户的唯一标识： column属性指定的内容：用户根据id查询时，所需要的参数的值 --> <association property="user" column="uid" javaType="user" select="com.itheima.dao.IUserDao.findById"></association> </resultMap> <!-- 查询所有 --> <select id="findAll" resultMap="accountUserMap"> select * from account </select> <!-- 根据用户id查询账户列表 --> <select id="findAccountByUid" resultType="account"> select * from account where uid = #{uid} </select> </mapper>
SqlMapConfig.xml
<?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> <!-- 配置properties--> <properties resource="jdbcConfig.properties"></properties> <!--配置参数--> <settings> <!--开启Mybatis支持延迟加载--> <setting name="lazyLoadingEnabled" value="true"/> <setting name="aggressiveLazyLoading" value="false"></setting> </settings> <!--使用typeAliases配置别名，它只能配置domain中类的别名 --> <typeAliases> <package name="com.itheima.domain"></package> </typeAliases> <!--配置环境--> <environments default="mysql"> <!-- 配置mysql的环境--> <environment id="mysql"> <!-- 配置事务 --> <transactionManager type="JDBC"></transactionManager> <!--配置连接池--> <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> <!-- 配置映射文件的位置 --> <mappers> <package name="com.itheima.dao"></package> </mappers> </configuration>
2.多对多实现延迟加载
IUserDao.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.itheima.dao.IUserDao"> <!-- 定义User的resultMap--> <resultMap id="userAccountMap" type="user"> <id property="id" column="id"></id> <result property="username" column="username"></result> <result property="address" column="address"></result> <result property="sex" column="sex"></result> <result property="birthday" column="birthday"></result> <!-- 配置user对象中accounts集合的映射 -->
(批注：在映射配置文件中 调用相关联的一方的根据id查询的方法) <collection property="accounts" ofType="account" select="com.itheima.dao.IAccountDao.findAccountByUid" column="id"></collection> </resultMap> <!-- 查询所有 --> <select id="findAll" resultMap="userAccountMap"> select * from user </select> <!-- 根据id查询用户 --> <select id="findById" parameterType="INT" resultType="user"> select * from user where id = #{uid} </select> </mapper>
三、Mybatis中的缓存
1.测试一级缓存
/** * 测试一级缓存 */ @Test public void testFirstLevelCache(){ User user1 = userDao.findById(41); System.out.println(user1); // sqlSession.close(); //再次获取SqlSession对象 // sqlSession = factory.openSession(); sqlSession.clearCache();//此方法也可以清空缓存 userDao = sqlSession.getMapper(IUserDao.class); User user2 = userDao.findById(41); System.out.println(user2); System.out.println(user1 == user2); }
一级缓存是SqlSession范围的缓存，当调用SqlSession的修改，添加，删除，commit()，close()等方法时，就会清空一级缓存。
2.测试二级缓存
第一步：让Mybatis框架支持二级缓存（在SqlMapConfig.xml中配置）
<?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> <!-- 配置properties--> <properties resource="jdbcConfig.properties"></properties> <settings> <setting name="cacheEnabled" value="true"/> </settings> <!--使用typeAliases配置别名，它只能配置domain中类的别名 --> <typeAliases> <package name="com.itheima.domain"></package> </typeAliases> <!--配置环境--> <environments default="mysql"> <!-- 配置mysql的环境--> <environment id="mysql"> <!-- 配置事务 --> <transactionManager type="JDBC"></transactionManager> <!--配置连接池--> <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> <!-- 配置映射文件的位置 --> <mappers> <package name="com.itheima.dao"></package> </mappers> </configuration>
第二步：让当前的映射文件支持二级缓存（在IUserDao.xml中配置）
第三步：让当前的操作支持二级缓存（在select标签中配置）
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.itheima.dao.IUserDao"> <!--开启user支持二级缓存 默认为true--> <cache/> <!-- 查询所有 --> <select id="findAll" resultType="user"> select * from user </select> <!-- 根据id查询用户 --> <select id="findById" parameterType="INT" resultType="user" useCache="true"> select * from user where id = #{uid} </select> <!-- 更新用户信息--> <update id="updateUser" parameterType="user"> update user set username=#{username},address=#{address} where id=#{id} </update> </mapper>
四、Mybatis中的注解开发
1.环境搭建
2.单表CRUD操作（代理Dao方式）
sqlMapConfig.xml
<?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>
或者
<package name="com.itheima.dao"></package>
</mappers> </configuration>
IUserDao
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; /** * 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(); }
3.多表查询操作
使用注解来解决实体类属性与数据库表列名对应不上的问题
/** * 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"), }) List<User> findAll();
mybatis注解开发一对一的查询配置
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
package com.itheima.dao; import com.itheima.domain.User; import org.apache.ibatis.annotations.*; import org.apache.ibatis.mapping.FetchType; import java.util.List; @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("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); }
4. 缓存的配置
第一步：让Mybatis框架支持二级缓存（在SqlMapConfig.xml中配置）
<?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> <!--配置开启二级缓存--> <settings> <setting name="cacheEnabled" value="true"/> </settings> <!--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> <package name="com.itheima.dao"></package> </mappers> </configuration>
第二步：让当前的操作支持二级缓存（在select标签中配置）
@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();
测试方法
@Test public void testFindOne(){ SqlSession session = factory.openSession(); IUserDao userDao = session.getMapper(IUserDao.class); User user = userDao.findById(57); System.out.println(user); session.close();//释放一级缓存 SqlSession session1 = factory.openSession();//再次打开session IUserDao userDao1 = session1.getMapper(IUserDao.class); User user1 = userDao1.findById(57); System.out.println(user1); session1.close(); }
标签：iat ring family enable lazyload actor 一级缓存 不能 tran
原文地址：https://www.cnblogs.com/lsk-130602/p/12202311.html
