Mybatis学习_06mybatis基于注解开发环境搭建单表多表操作二级缓存

本文链接：https://blog.youkuaiyun.com/chenchen818/article/details/102257935
本文详细介绍了在MyBatis框架中使用注解进行环境搭建、单表及多表查询操作的过程，包括实体类定义、DAO接口设计及测试类实现，同时探讨了一级与二级缓存的配置与应用。
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                    Mybatis中的注解开发
环境搭建
maven导包<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.itheima</groupId>
    <artifactId>day04_eesy_04annoOne2Many</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>

</project>

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

    <!--配置实体类别名-->
    <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>


单表CRUD操作(代理DAO)+多表查询操作
实体类(账户类+用户类)public class Account implements Serializable {

    private Integer id;
    private Integer uid;
    private Double money;

    //多对一（mybatis中称之为一对一）的映射：一个账户只能属于一个用户
    private User user;
}
public class User implements Serializable{

    private Integer userId;
    private String userName;
    private String userAddress;
    private String userSex;
    private Date userBirthday;

    //一对多关系映射：一个用户对应多个账户
    private List<Account> accounts;
}
+ 接口类
```java
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);
}

@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);


}

测试类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  testFindAll(){
        List<User> users = userDao.findAll();
//        for(User user : users){
//            System.out.println("---每个用户的信息----");
//            System.out.println(user);
//            System.out.println(user.getAccounts());
//        }
    }

    @Test
    public void testFindOne(){
        User user = userDao.findById(57);
        System.out.println(user);
    }

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

}
public class AccountTest {
    private InputStream in;
    private SqlSessionFactory factory;
    private SqlSession session;
    private IAccountDao accountDao;

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

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

    @Test
    public  void  testFindAll(){
        List<Account> accounts = accountDao.findAll();
        for(Account account : accounts){
            System.out.println("----每个账户的信息-----");
            System.out.println(account);
            System.out.println(account.getUser());
        }
    }

}


缓存的配置
一级缓存不用开，自动开启
二级缓存先在总配置文件开启<settings><setting name="cacheEnabled" value="true"/></settings>，再在dao类里类名上面加注解@CacheNamespace(blocking = true)
二级缓存测试类public class SecondLevelCatchTest {

    private InputStream in;
    private SqlSessionFactory factory;


    @Before
    public  void init()throws Exception{
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        factory = new SqlSessionFactoryBuilder().build(in);

    }

    @After
    public  void destroy()throws  Exception{

        in.close();
    }

    @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();

    }
}




                