Mybatis学习——基本增删改查(CRUD)

Eclipse+Mybatis+MySql

　　1.所需jar

　　2.项目目录

　　3.源代码

 package com.zhengbin.entity;

 public class Student {
     private int id;
     private String name;
     private double score;
     @Override
     public String toString() {
         return "Student [id=" + id + ", name=" + name + ", score=" + score + "]";
     }
     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public double getScore() {
         return score;
     }
     public void setScore(double score) {
         this.score = score;
     }
     public Student(int id, String name, double score) {
         super();
         this.id = id;
         this.name = name;
         this.score = score;
     }
     // *注意这个必须加
     public Student() {
         super();
     }
 }

Student.java

 <?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">
 <!-- 每个映射文件的namespace应该是唯一的 -->
 <mapper namespace="com.zhengbin.entity.studentMapper">
     <!-- parameterType 参数表示需要参数的类型 -->
     <!-- resultType 参数表示返回结果的类型，该可以写为实体包的全路径，或者在conf.xml配置文件中，声明实体的别名 -->
     <select id="getStudent" parameterType="int" resultType="Student">
         select * from student where id=#{id}
     </select>

     <select id="getAllStudent" resultType="Student">
         select * from student
     </select>

     <insert id="addStudent" parameterType="Student">
         insert into student(name,score) values(#{name},#{score})
     </insert>

     <update id="updateStudent" parameterType="Student">
         update student set name=#{name},score=#{score} where id=#{id}
     </update>

     <delete id="deleteStudent" parameterType="int">
         delete from student where id=#{id}
     </delete>
 </mapper>

studentMapper.xml

 package com.zhengbin.entity2;

 import org.apache.ibatis.annotations.Select;

 import com.zhengbin.entity.Student;

 public interface studentMapper {
     @Select("select * from student where id=#{id}")
     public Student testGet(int id);
 }

studentMapper.java

 package com.zhengbin.test;

 import java.util.List;

 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;

 import com.zhengbin.entity.Student;
 import com.zhengbin.util.MyBatisUtils;

 public class Test {
     @org.junit.Test
     public void testGet(){
         SqlSessionFactory sessionFactory = MyBatisUtils.getFactory();
         // 参数为TRUE，相当于session.commit();
         SqlSession session = sessionFactory.openSession(true);
         // 读取映射文件
         String statement = "com.zhengbin.entity.studentMapper" + ".getStudent";
         Student s = session.selectOne(statement,5);
         System.out.println(s);
         session.close();
     }

     @org.junit.Test
     public void testGetAll(){
         SqlSessionFactory sessionFactory = MyBatisUtils.getFactory();
         // 参数为TRUE，相当于session.commit();
         SqlSession session = sessionFactory.openSession(true);
         // 读取映射文件
         String statement = "com.zhengbin.entity.studentMapper" + ".getAllStudent";
         List<Student> list = session.selectList(statement);
         System.out.println(list);
         session.close();
     }

     @org.junit.Test
     public void testAdd(){
         SqlSessionFactory sessionFactory =  MyBatisUtils.getFactory();
         SqlSession session = sessionFactory.openSession(true);
         String statement = "com.zhengbin.entity.studentMapper" + ".addStudent";
         Student s = new Student();
         s.setName("zhengB");
         s.setScore(95.9);
         int insert = session.insert(statement, s);
         System.out.println(insert);
         session.close();
     }

     @org.junit.Test
     public void testUpdate(){
         SqlSessionFactory sessionFactory = MyBatisUtils.getFactory();
         SqlSession session = sessionFactory.openSession(true);
         String statement = "com.zhengbin.entity.studentMapper" + ".updateStudent";
         Student s = new Student();
         s.setId(14);
         s.setName("zhengbin");
         s.setScore(96);
         int update = session.update(statement, s);
         System.out.println(update);
         session.close();
     }

     @org.junit.Test
     public void testDelete(){
         SqlSessionFactory sessionFactory = MyBatisUtils.getFactory();
         SqlSession session = sessionFactory.openSession(true);
         String statement = "com.zhengbin.entity.studentMapper" + ".deleteStudent";
         int delete = session.delete(statement,21);
         System.out.println(delete);
         session.close();
     }
 }

Test.java

 package com.zhengbin.test;

 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;

 import com.zhengbin.entity.Student;
 import com.zhengbin.entity2.studentMapper;
 import com.zhengbin.util.MyBatisUtils;

 public class Test2 {
     @org.junit.Test
     public void testGet(){
         SqlSessionFactory sessionFactory = MyBatisUtils.getFactory();
         SqlSession session = sessionFactory.openSession(true);
         studentMapper mapper = session.getMapper(studentMapper.class);
         Student s = mapper.testGet(14);
         System.out.println(s);
         session.close();
     }
 }

Test2.java

 package com.zhengbin.util;

 import java.io.InputStream;

 import org.apache.ibatis.session.SqlSessionFactory;
 import org.apache.ibatis.session.SqlSessionFactoryBuilder;

 public class MyBatisUtils {
     public static SqlSessionFactory getFactory(){
         String resource = "conf.xml";
         InputStream is = MyBatisUtils.class.getClassLoader().getResourceAsStream(resource);
         SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
         return sessionFactory;
     }
 }

MyBatisUtils.java

 <?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>
     <!-- 数据库配置文件 -->
      <properties resource="jdbc.properties"/>
      <!-- 取别名 -->
      <typeAliases>
          <!-- 方式一、为类取别名 -->
          <!-- <typeAlias type="com.zhengbin.entity.Student" alias="_Student"/> -->
          <!-- 方式二、自动以类名为别名 -->
          <package name="com.zhengbin.entity"/>
      </typeAliases>
     <!--
         development : 开发模式
         work : 工作模式
      -->
     <environments default="development">
         <environment id="development">
             <transactionManager type="JDBC" />
             <dataSource type="POOLED">
                 <property name="driver" value="${driver}" />
                 <property name="url" value="${url}" />
                 <property name="username" value="${username}" />
                 <property name="password" value="${password}" />
             </dataSource>
         </environment>
     </environments>
     <mappers>
         <!-- 这是一个路径的结构，不是包的结构 -->
         <mapper resource="com/zhengbin/entity/studentMapper.xml"/>
         <mapper class="com.zhengbin.entity2.studentMapper"/>
     </mappers>
 </configuration>

conf.xml

 driver=com.mysql.jdbc.Driver
 url=jdbc:mysql://localhost:3307/student
 username=root
 password=950906

jdbc.properties

 <?xml version="1.0" encoding="UTF-8" ?>
 <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
 <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
     <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
         <layout class="org.apache.log4j.PatternLayout">
             <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m (%F:%L) \n" />
         </layout>
     </appender>
     <logger name="java.sql">
         <level value="debug" />
     </logger>
     <logger name="org.apache.ibatis">
         <level value="debug" />
     </logger>
     <root>
         <level value="debug" />
         <appender-ref ref="STDOUT" />
     </root>
 </log4j:configuration>

log4j.xml

　　4.遇到的问题

(1)奇怪的junit：如果新建一个class，名为Test则可能出现不能使用注解@Test的情况，此时用@org.junit.Test即可，或者更改class名，不以Test开头 好奇葩

(2)实体类必须要加superclass，否则报错，因为MyBatis无法通过配置文件找到实体类