mybatis利用代理DAO實現CRUD操作

mybatis實現CRUD操作

注：數據庫字段名和實體類屬性名最好是一致的。如果兩端不一致，造成mybatis無法填充對應的字段信息。解決方法(見後文)

數據庫設計

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for user
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(32) NOT NULL COMMENT '用戶名稱',
  `birthday` datetime DEFAULT NULL COMMENT '生日',
  `sex` char(1) DEFAULT NULL COMMENT '性別',
  `address` varchar(256) DEFAULT NULL COMMENT '地址',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=57 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES ('41', '老王', '2018-02-27 17:47:08', '男', '北京');
INSERT INTO `user` VALUES ('42', '小二王', '2018-03-02 15:09:37', '女', '北京金燕龍');
INSERT INTO `user` VALUES ('43', '小二王', '2018-03-04 11:34:34', '女', '北京金燕龍');
INSERT INTO `user` VALUES ('45', '傳智播客', '2018-03-04 12:04:06', '男', '北京金燕龍');
INSERT INTO `user` VALUES ('46', '老王', '2018-03-07 17:37:26', '男', '北京');

導入依賴包

實現mybatis僅需mybatis和mysql-connect-java的包，小編這裏另外導入log4j和junit是爲了方便調試。

<?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.gohb</groupId>
    <artifactId>mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>


    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.4</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>


</project>

爲log4j設置輸出內容

log4j.properties

log4j.rootLogger=debug, stdout, R

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=%5p - %m%n

log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=firestorm.log

log4j.appender.R.MaxFileSize=100KB
log4j.appender.R.MaxBackupIndex=1

log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n

log4j.logger.com.codefutures=DEBUG

User.java

package com.gohb.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;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", address='" + address + '\'' +
                ", sex='" + sex + '\'' +
                ", birthday=" + 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;
    }
}

QueryVo.java

package com.gohb.domain;

public class QueryVo {

    private User user;

    public User getUser() {
        return user;
    }

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

前期準備工作完成

最終目錄結構如下：

MyBatis使用大致步驟總結

1)配置mybatis-config.xml 全局的配置文件 (1、數據源，2、外部的mapper)
2)創建SqlSessionFactory
3)通過SqlSessionFactory創建SqlSession對象
4)通過SqlSession操作數據庫 CRUD
5)調用session.commit()提交事務
6)調用session.close()關閉會話

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>
    <!--配置環境-->
    <environments default="development">
        <environment id="development">
            <!--配置事物-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置連接池-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/eesy_mybatis?useUnicode=true&characterEncoding=UTF-8" />
                <property name="username" value="root" />
                <property name="password" value="12345" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/gohb/dao/IUserDao.xml"/>
    </mappers>
</configuration>

IUserDao.java

package com.gohb.dao;

import com.gohb.domain.QueryVo;
import com.gohb.domain.User;

import java.util.List;

public interface IUserDao {

    //查詢所有
    List<User> findAll() throws Exception;

    //保存用戶
    void saveUser(User user) throws Exception;

    //更新用戶
    void updateUser(User user) throws Exception;

    //根據ID刪除用戶
    void deleteUser(Integer userId) throws Exception;

    //根據ID查詢用戶信息
    User findById(Integer userId) throws Exception;

    //根據名稱模糊查詢用戶姓名
    List<User> findByName(String name)throws Exception;

    //查詢總記錄條數
    int findTotal() throws Exception;
    
    //根據queryVo中的條件查詢用戶
    List<User> findUserByVo(QueryVo vo)throws Exception;
}

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.gohb.dao.IUserDao">
    <!--查詢所有-->
    <select id="findAll" resultType="com.gohb.domain.User">
        select * from user
    </select>
    <!--保存用戶-->
    <insert id="saveUser" parameterType="com.gohb.domain.User">
        <!--配置插入操作後，獲取插入數據的id-->
        <!--id：唯一標識，隨便寫，在同一個命名空間下保持唯一，使用動態代理之後要求和方法名保持一致
            parameterType：參數的類型，使用動態代理之後和方法的參數類型一致
            useGeneratedKeys:開啓主鍵回寫
            keyColumn：指定數據庫的主鍵
            keyProperty：主鍵對應的實體類屬性名-->
        <selectKey keyProperty="id" keyColumn="id" resultType="int" order="AFTER">
            select last_insert_id();
        </selectKey>
        insert into user(username,address,sex,birthday) values (#{username},#{address},#{sex},#{birthday})
    </insert>
    <!--更新用戶-->
    <update id="updateUser" parameterType="com.gohb.domain.User">
        update user set username=#{username},address=#{address},sex=#{sex},birthday=#{birthday} where id=#{id}
    </update>
    <!--根據id刪除用戶-->
    <delete id="deleteUser" parameterType="java.lang.Integer">
        delete from user where id=#{uid}
    </delete>
    <!--根據id查詢用戶-->
    <select id="findById" parameterType="INT" resultType="com.gohb.domain.User">
        select * from user where id=#{id}
    </select>
    <!--根據姓名模糊查詢-->
    <select id="findByName" parameterType="String" resultType="com.gohb.domain.User">
        <!--select * from user where username like '%${username}%'-->
        select * from user where username like "%"#{username}"%"
    </select>
    <!--查詢總記錄條數-->
    <select id="findTotal" resultType="INT">
        select count(id) from user
    </select>
    <!--根據queryVo的條件查詢用戶-->
    <select id="findUserByVo" parameterType="com.gohb.domain.QueryVo" resultType="com.gohb.domain.User">
        select * from user where username like "%"#{user.username}"%"
    </select>

</mapper>

測試類編寫

package com.gohb;

import com.gohb.dao.IUserDao;
import com.gohb.domain.QueryVo;
import com.gohb.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;

public class test {

    private InputStream in;
    private SqlSession sqlSession;
    private IUserDao userDao;

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

    @After
    public void destory()throws Exception{
        sqlSession.close();
        in.close();
    }


    /**
     * 測試查詢所有
     */
    @Test
    public void testFindAll() throws Exception{
        List<User> users = userDao.findAll();
        for (User user :
                users) {
            System.out.println(user);
        }
    }

    /**
     * 測試保存操作
     */
    @Test
    public void testSave() throws Exception{
        User user = new User();
        user.setId(41);
        user.setUsername("gohb");
        user.setAddress("北京");
        user.setSex("男");
        user.setBirthday(new Date());
        userDao.saveUser(user);
        sqlSession.commit();
        System.out.println(user);
    }

    /**
     * 更新用戶
     */
    @Test
    public void testUpdate() throws Exception{
        User user = new User();
        user.setId(51);
        user.setUsername("gohbupdate");
        user.setAddress("北京");
        user.setSex("女");
        user.setBirthday(new Date());
        userDao.updateUser(user);
        sqlSession.commit();
    }
    /**
     *  根據id刪除
     */
    @Test
    public void testDelete()throws Exception{
        userDao.deleteUser(48);
        sqlSession.commit();
    }

    /**
     *  根據id查詢
     */
    @Test
    public void testFindOne()throws Exception{
        User user = userDao.findById(46);
        sqlSession.commit();
        System.out.println(user);
    }

    /**
     *  根據姓名模糊查詢
     */
    @Test
    public void testFindByName()throws Exception{
        List<User> users = userDao.findByName("gohb");
        for (User user:
            users) {
            System.out.println(user);
        }
        sqlSession.commit();
    }

    /**
     * 查詢總記錄條數
     */
    @Test
    public void testFindTotal()throws Exception{
        int total = userDao.findTotal();
        System.out.println(total);
    }

    /**
     *  根據QueryVo作爲查詢條件
     */
    @Test
    public void testFindByQueryVo()throws Exception{
        QueryVo vo = new QueryVo();
        User user = new User();
        user.setUsername("gohb");
        vo.setUser(user);
        List<User> users = userDao.findUserByVo(vo);
        for (User u:
                users) {
            System.out.println(u);
        }
        sqlSession.commit();
    }

}

SqlSessionFactoryBuilder創建工廠使用了構建者模式，把對象的創建細節隱藏，使使用者直接調用方法即可拿到對象。
factory.openSession()生成sqlSession使用了工廠模式。優勢：解耦（降低類之間的依賴關係）
sqlSession.getMapper(IUserDao.class)創建Dao接口實現類使用代理模式。優勢：不修改源碼的基礎上對已有方法進行增強

關於數據庫字段名和實體類屬性名不一致的解決方法

假設實體類User的屬性如下：

1.在sql語句中使用別名

2.利用mybatis本身，配置查詢結果列名和實體類屬性的對應關係

    <!--配置查詢結果列名和實體類屬性的對應關係-->
    <!--id：唯一標識，隨便寫-->
    <resultMap id="userMap" type="com.gohb.domain.User">
        <!--主鍵字段的對應-->
        <!--property：主鍵對應的實體類屬性
            column：指定數據庫的主鍵-->
        <id property="userId" column="id"></id>
        <!--非主鍵字段的對應-->
        <result property="userName" column="username"></result>
        <result property="userAddress" column="address"></result>
        <result property="userSex" column="sex"></result>
        <result property="userBirthday" column="birthday"></result>
    </resultMap>
    <!--查詢所有-->
    <select id="findAll" resultMap="userMap">
        select * from user
    </select>

mybatis利用代理DAO實現CRUD操作

mybatis實現CRUD操作

數據庫設計

導入依賴包

log4j.properties

User.java

QueryVo.java

最終目錄結構如下：

MyBatis使用大致步驟總結

SqlMapConfig.xml

IUserDao.java

IUserDao.xml

測試類編寫

關於數據庫字段名和實體類屬性名不一致的解決方法

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