MyBatis 安装和配置

　　在这里我们使用 MyBatis 开发一个简单的 Java 项目（默认你已安装JDK和MySQL及会使用Maven的基本操作），可以与上一篇通过底层操作数据进行比较

1、新建表 students，插入数据

SQL Code

 CREATE TABLE students(
      stud_id INT(11) NOT NULL AUTO_INCREMENT,
      stud_name VARCHAR(50) NOT NULL,
      stud_email VARCHAR(50) NOT NULL,
      stud_dob DATE DEFAULT NULL,
      PRIMARY KEY (stud_id)
 ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;

 INSERT INTO students(stud_id,stud_name,stud_email,stud_dob)
 VALUES (1,'Student1','student1@qq.com','1992-01-01');
 INSERT INTO students(stud_id,stud_name,stud_email,stud_dob)
 VALUES (2,'Student2','student2@qq.com','1993-12-31');

2、新建一个Maven项目，在pom.xml中引入Mybatis.jar

2.1 创建Maven项目，名为HzMyBatis

2.2 在pom.xml中引入相应的jar包

pom.xml code

 <dependencies>
      <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.11</version>
        <scope>test</scope>
      </dependency>
      <dependency>
          <groupId>org.projectlombok</groupId>
          <artifactId>lombok</artifactId>
          <version>1.18.2</version>
          <scope>provided</scope>
      </dependency>
      <dependency>
          <groupId>mysql</groupId>
          <artifactId>mysql-connector-java</artifactId>
          <version>5.1.39</version>
      </dependency>
      <dependency>
          <groupId>org.mybatis</groupId>
          <artifactId>mybatis</artifactId>
          <version>3.4.1</version>
      </dependency>
     <!-- 日志框架 -->
      <dependency>
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-api</artifactId>
          <version>1.7.25</version>
      </dependency>
      <dependency>
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-log4j12</artifactId>
          <version>1.7.25</version>
          <scope>test</scope>
      </dependency>
      <dependency>
          <groupId>log4j</groupId>
          <artifactId>log4j</artifactId>
          <version>1.2.17</version>
      </dependency>
    </dependencies>

说明：mysql-connector-java-5.1.39 mysql数据库的驱动包、mybatis-3.4.1 Mybatis包、lombok-1.18.2 减少重复代码量（getter/setter/toString等需要注解标注）

3、新建 mybatis-config.xml 和映射器 StudentMapper.xml 配置文件

mybatis-config.xml:包括数据库连接信息，类型别名等信息

StudentMapper.xml:映射的SQL语句

这两个xml文件需要放到classpath路径下

mybatis-config.xml Code

 <?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>
      <!-- 设置Bean别名 -->
      <typeAliases>
          <typeAlias alias="Student" type="com.hz.mybatis.bean.Student" />
      </typeAliases>

      <!-- 设置当前环境 -->
      <environments default="development">
          <environment id="development">
              <!-- 开启事务 JDBC使用数据库自己的事务（局部事务） -->
              <transactionManager type="JDBC" />
              <dataSource type="POOLED">
                  <property name="driver" value="com.mysql.jdbc.Driver" />
                  <property name="url" value="jdbc:mysql://127.0.0.1:3306/hadoop" />
                  <property name="username" value="root" />
                  <property name="password" value="root" />
              </dataSource>
          </environment>
      </environments>

      <!-- 映射文件路径 -->
      <mappers>
          <mapper resource="com/hz/mybatis/mapper/StudentMapper.xml" />
      </mappers>
 </configuration>

StudentMapper.xml Code

 <?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.hz.mybatis.mapper.StudentMapper">
     <resultMap type="Student" id="StudentResult">
         <id property="studId" column="stud_id" />
         <result property="name" column="stud_name" />
         <result property="email" column="stud_email" />
         <result property="dob" column="stud_dob" />
     </resultMap>

     <select id="findAllStudents" resultMap="StudentResult">
         SELECT * FROM STUDENTS
     </select>

     <select id="findStudentById" parameterType="java.lang.Integer" resultType="Student">
         SELECT STUD_ID AS STUDID, STUD_NAME AS NAME, STUD_EMAIL AS EMAIL, STUD_DOB AS DOB FROM STUDENTS WHERE STUD_ID = #{Id}
     </select>

     <insert id="insertStudent" parameterType="Student">
         INSERT INTO STUDENTS(STUD_ID, STUD_NAME,STUD_EMAIL,STUD_DOB)
         VALUES(#{studId}, #{name}, #{email}, #{dob})
     </insert>
 </mapper>

3、新建 MyBatisSqlSessionFactory 单例模式类

MyBatisSqlSessionFactory.java Code

import java.io.InputStream;

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

/**
  * 创建单例SqlSessionFactory
  * @author DONG
  *
  */
public class MyBatisSqlSessionFactory {

    private static SqlSessionFactory sqlSessionFactory;

     public static SqlSessionFactory getSqlSessionFactory(){
         if (sqlSessionFactory == null) {
             InputStream inputStream;
             try {
                 inputStream = Resources.getResourceAsStream("mybatis-config.xml");
                 sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
             } catch (Exception e) {
                 e.printStackTrace();
             }
         }
         return sqlSessionFactory;
     }
}

4、新建映射器 StudentMapper 接口和 StudentService 类

创建一个 StudentMapper 接口，其定义的方法名和在 Mapper XML 配置文件定义的 SQL 映射语 句名称相同

创建一个 StudentService.java 类，包含了一些业务操作的实现

1、首先, 创建 JavaBean Student.java

Student.java Code

 import java.util.Date;

 import lombok.Data;

 @Data
 public class Student {

     private Integer studId;
      private String name;
      private String email;
      private Date dob;

 }

2、创建映射器 Mapper 接口 StudentMapper.java 其方法签名和 StudentMapper.xml 中定义的 SQL 映射定义名
相同

StudentMapper.java Code

 import java.util.List;

 import com.hz.mybatis.bean.Student;

 public interface StudentMapper {
      List<Student> findAllStudents();
      Student findStudentById(Integer id);
      void insertStudent(Student student);
 }

3、现在创建 MyBatisStudentService.java 实现对表 students 的数据库操作

 import java.util.List;

 import org.apache.ibatis.session.SqlSession;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 import com.hz.mybatis.bean.Student;
 import com.hz.mybatis.mapper.StudentMapper;
 import com.hz.mybatis.util.MyBatisSqlSessionFactory;

 /**
   * 学生业务操作
   * @author DONG
   *
   */
 public class MyBatisStudentService {

      private static Logger logger = LoggerFactory.getLogger(MyBatisStudentService.class);

     /**
       * 查询所有学生信息
       * @return
       */
      public List<Student> findAllStudents(){
          SqlSession sqlSession = MyBatisSqlSessionFactory.openSession();
          logger.debug("获取sqlSession信息: ", sqlSession);
          try {
              StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
              return studentMapper.findAllStudents();
          } finally {
              sqlSession.close();
          }
      }

      /**
       * 通过学生ID查询学生信息
       * @param studId
       * @return
       */
      public Student findStudentById(Integer studId){
          logger.debug("通过学生ID查询学生信息: ", studId);

          SqlSession sqlSession = MyBatisSqlSessionFactory.openSession();

          try {
              StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
              return studentMapper.findStudentById(studId);
          } finally {
              sqlSession.close();
          }
      }

      /**
       * 插入学生信息
       */
      public void insertStudent(Student student){
          SqlSession sqlSession = MyBatisSqlSessionFactory.openSession();

          try {
              StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
              studentMapper.insertStudent(student);
          } finally {
              sqlSession.close();
          }

      }
 }

5、新建一个 JUnit 测试类来测试 MyBatisStudentService

 import java.util.List;

 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;

 import com.hz.mybatis.bean.Student;
 import com.hz.mybatis.service.MyBatisStudentService;

 /**
   * 测试
   * @author DONG
   *
   */
 public class TestStudentMapper {

     private static MyBatisStudentService studentService;

      @BeforeClass
      public static void setup(){
          studentService = new MyBatisStudentService();
      }

      @AfterClass
      public static void teardown(){
          studentService = null;
      }

      @Test
      public void testFindAllStudents(){
          List<Student> students = studentService.findAllStudents();

          for (Student student : students) {
              System.out.println(student);
          }
      }
 }