MyBatis_注解开发_hehe.employment.over.32.2

其他 2021-03-21 07:01:15 阅读次数: 0

文章目录

32.7 mybatis注解开发的环境搭建

  • 在pom.xml中导入坐标：
<?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.xww</groupId>
    <artifactId>day32_mybatis3</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>
  • 创建实体类User
package com.xww.domain;

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable{
    
    

    private Integer id;
    private String username;
    private String address;
    private String sex;
    private Date birthday;

    public Integer getId() {
    
    
        return id;
    }

    public void setId(Integer id) {
    
    
        this.id = id;
    }

    public String getUsername() {
    
    
        return username;
    }

    public void setUsername(String username) {
    
    
        this.username = username;
    }

    public String getAddress() {
    
    
        return address;
    }

    public void setAddress(String address) {
    
    
        this.address = address;
    }

    public String getSex() {
    
    
        return sex;
    }

    public void setSex(String sex) {
    
    
        this.sex = sex;
    }

    public Date getBirthday() {
    
    
        return birthday;
    }

    public void setBirthday(Date birthday) {
    
    
        this.birthday = birthday;
    }

    @Override
    public String toString() {
    
    
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", address='" + address + '\'' +
                ", sex='" + sex + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}
  • 创建IUserDao接口
package com.xww.dao;

import com.xww.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();
}
  • 准备主配置文件，SqlMapConfig.xml 如下：
<?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.xww.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.xww.dao.IUserDao"></mapper>
    </mappers>
</configuration>

package com.xww.test;

import com.xww.dao.IUserDao;
import com.xww.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("注解");
        user.setAddress("2021.2.26日很焦急");

        userDao.saveUser(user);
    }

    @Test
    public void testUpdate(){
    
    
        User user = new User();
        user.setId(57);
        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(57);
        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);
    }
}

32.8 mybatis注解建立实体类属性和数据库表中列的对应关系

  • 如果字段和属性对应不上，可以使用别名解决，也可以使用注解映射的方式解决，如下：
    • 修改IUserDao接口中的查询方法中的注解
package com.xww.dao;

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

import java.util.List;
/**
 * 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")
    })
    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);


}

32.9 mybatis注解开发一对一的查询配置

  • 1.创建一个实体类Account
  • 2.创建IAccountDao接口，并添加查询所有的方法，查询account的同时需要查询用户信息,首先修改accont的类
package com.xww.domain;

import java.io.Serializable;

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 User getUser() {
    
    
        return user;
    }

    public void setUser(User user) {
    
    
        this.user = user;
    }

    public Integer getId() {
    
    
        return id;
    }

    public void setId(Integer id) {
    
    
        this.id = id;
    }

    public Integer getUid() {
    
    
        return uid;
    }

    public void setUid(Integer uid) {
    
    
        this.uid = uid;
    }

    public Double getMoney() {
    
    
        return money;
    }

    public void setMoney(Double money) {
    
    
        this.money = money;
    }

    @Override
    public String toString() {
    
    
        return "Account{" +
                "id=" + id +
                ", uid=" + uid +
                ", money=" + money +
                '}';
    }
}
  • 3.IAccountDao接口，并设置延迟查询策略为不延迟
package com.xww.dao;


import com.xww.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;

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.xww.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);
}
  • 4.测试

    @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());
      }
    }

32.10 mybatis注解开发一对多的查询配置

  • 修改User实体类
package com.xww.domain;

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

/**
 * @author 黑马程序员
 * @Company http://www.ithiema.com
 */
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;

    public List<Account> getAccounts() {
    
    
        return accounts;
    }

    public void setAccounts(List<Account> accounts) {
    
    
        this.accounts = accounts;
    }
    public Integer getUserId() {
    
    
        return userId;
    }

    public void setUserId(Integer userId) {
    
    
        this.userId = userId;
    }

    public String getUserName() {
    
    
        return userName;
    }

    public void setUserName(String userName) {
    
    
        this.userName = userName;
    }

    public String getUserAddress() {
    
    
        return userAddress;
    }

    public void setUserAddress(String userAddress) {
    
    
        this.userAddress = userAddress;
    }

    public String getUserSex() {
    
    
        return userSex;
    }

    public void setUserSex(String userSex) {
    
    
        this.userSex = userSex;
    }

    public Date getUserBirthday() {
    
    
        return userBirthday;
    }

    public void setUserBirthday(Date userBirthday) {
    
    
        this.userBirthday = userBirthday;
    }

    @Override
    public String toString() {
    
    
        return "User{" +
                "userId=" + userId +
                ", userName='" + userName + '\'' +
                ", userAddress='" + userAddress + '\'' +
                ", userSex='" + userSex + '\'' +
                ", userBirthday=" + userBirthday +
                '}';
    }
}
  • 修改IUserDao接口中的方法，并指明为延迟加载
package com.xww.dao;

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

import java.util.List;
/**
 * 在mybatis中针对,CRUD一共有四个注解
 *  @Select @Insert @Update @Delete
 */
//开启二级缓存
@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.xww.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);


}

32.11 mybatis注解开发使用二级缓存

  • 修改主配置文件，开启二级缓存
    <!--配置开启二级缓存-->
    <settings>
        <setting name="cacheEnabled" value="true"/>
    </settings>
  • 在接口中添加一个注解开启二级缓存
//开启二级缓存
@CacheNamespace(blocking = true)
public interface IUserDao {
  • 测试代码
    @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();
    }

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