用JavaSE简单入门MyBatis连接MySQL…，javasemybatis

来源： javaer 分享于 2019-06-08 点击 17091 次点评：130

用JavaSE简单入门MyBatis连接MySQL…，javasemybatis

在Netbeans中新建一个 Java——Java应用程序项目，其目录结构如下：

需要准备和下载的jar库： 1、mybatis-3.4.1.jar 2、mysql-connector-java-5.1.39-bin.jar（安装MySQL的时候，勾选安装Connector.J后会附带有，在MySQL 安装目录/Connector.J 5.1 里面）
添加好库后，就可以开始干活了。首先得在MySQL里面建立数据库和表格：文件student.sql——不过这个文件并不参与MyBatis。我单独登录MySQL Client然后在命令行输入SQL语句创建的表格

CREATE DATABASE STUDENT_MANAGER; USE STUDENT_MANAGER;
CREATE TABLE STUDENT_TBL ( STUDENT_ID VARCHAR(255) PRIMARY KEY, STUDENT_NAME VARCHAR(10) NOT NULL, STUDENT_SEX VARCHAR(10), STUDENT_BIRTHDAY DATE, CLASS_ID VARCHAR(255) );
INSERT INTO STUDENT_TBL (STUDENT_ID, STUDENT_NAME, STUDENT_SEX, STUDENT_BIRTHDAY, CLASS_ID) VALUES (123456, '某某某', '女', '1980-08-01', 121546 )

创建完后数据库里面的内容，用MySQL Workbench查看：

然后我们开始编写类：首先，我们把这个STUDENT_TBL表的表头编写成一个POJO类（只含有成员变量，setter和getter的简单Java对象“Plain Ordinary Java Object”）文件StudentEntity.Java

package mybatishelloworld; import java.io.Serializable; import java.util.Date; public class StudentEntity implements Serializable { private static final long serialVersionUID = 3096154202413606831L; private Date studentBirthday; private String studentID; private String studentName; private String studentSex; public Date getStudentBirthday() { return studentBirthday; } public String getStudentID() { return studentID; } public String getStudentName() { return studentName; } public String getStudentSex() { return studentSex; } // Setter …… …… …… …… public void setStudentBirthday(Date studentBirthday) { this.studentBirthday = studentBirthday; } public void setStudentID(String studentID) { this.studentID = studentID; } public void setStudentName(String studentName) { this.studentName = studentName; } public void setStudentSex(String studentSex) { this.studentSex = studentSex; } public void println(){ System.out.print(this.studentID+" "); System.out.print(this.studentName+" "); System.out.print(this.studentSex+" "); System.out.println(this.studentBirthday); } }

其实为了方便演示，这个Java类并不纯粹，而是添加了个println方法便于打印SQL后的结果
接着我们建立一个Mapper接口——于是，我们为什么需要一个映射（Mapper）接口呢？原因我们看看代码就懂了：文件StudentMapper.java

package mybatishelloworld;
import java.util.List;
public interface StudentMapper { public StudentEntity getStudent(String studentID); public StudentEntity getStudentAndClass(String studentID); public List getStudentAll();
public void insertStudent(StudentEntity entity); public void deleteStudent(StudentEntity entity); public void updateStudent(StudentEntity entity); }

我们发现，这个接口里面都是方法名。按照常规的Java思维，要真正用接口，必须有方法的实现才行： public class StudentMapperImpl implements StudentMapper{ @Override public StudentEntity getStudent(String studentID) { StudentEntity se=SQL.get(studentID); //那个头疼啊，还像JDBC一样把SQL语句写到字符串里面？ } …………………… } 但是！但是的但是！这个具体的实现，在Mybatis里面，不需要我们写Java了。你可以把怎么用SQL语句get这个StudentEntity，写到一个xml文件里面。所以，这个接口Interface，就是用来映射XML文件里面的SQL查询语句的，如何把xml里的sql转换为java语句里的jdbc，交由MyBatis来完成。下面就是与之相对应的XML文件：文件StudentMapper.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="mybatishelloworld.StudentMapper">  <resultMap type="StudentEntity" id="studentResultMap"> <id property="studentID" column="STUDENT_ID"/> <result property="studentName" column="STUDENT_NAME"/> <result property="studentSex" column="STUDENT_SEX"/> <result property="studentBirthday" column="STUDENT_BIRTHDAY"/> </resultMap>  <select id="getStudent" parameterType="String" resultType="StudentEntity" resultMap="studentResultMap"> <![CDATA[ SELECT * from STUDENT_TBL ST WHERE ST.STUDENT_ID = #{studentID} ]]> </select>  <select id="getStudentAll" resultType="StudentEntity" resultMap="studentResultMap"> <![CDATA[ SELECT * from STUDENT_TBL ]]> </select> </mapper>

为了使用Mybatis，我们还得个它一个配置文件，配置所使用的数据库类型，数据库连接地址，用户名和密码等等，这个文件的配置如下：文件mybatis-config.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>  <typeAliases> <typeAlias alias="StudentEntity" type="mybatishelloworld.StudentEntity" /> </typeAliases> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/student_manager?useSSL=true"/> <property name="username" value="root"/> <property name="password" value="rootOfPasswd"/> </dataSource> </environment> </environments>  <mappers> <mapper resource="mybatishelloworld/StudentMapper.xml" /> </mappers> </configuration>

数据库驱动跟Hibernate里面一样，连接MySQL的话，用的是value=com.mysql.jdbc.Driver
最后我们在MainClass的main函数里面，测试我们的整个配置文件MainClass.java

package mybatishelloworld;
import java.io.IOException; import java.io.InputStream; import java.util.List; import java.util.logging.Level; import java.util.logging.Logger; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class MainClass { public static void main(String[] args) { String resource = "mybatishelloworld/mybatis-config.xml"; //告诉MyBatis核心配置文件在哪里 InputStream inputStream = null; try { inputStream = Resources.getResourceAsStream(resource); }catch(IOException ex){Logger.getLogger(MainClass.class.getName()).log(Level.SEVERE, null, ex);}
//打开SQL对话工厂 SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); try (SqlSession session = sqlSessionFactory.openSession()) { //用工厂生成一个对话 //这里是精华，session用getMapper方法从xml里面生成了StudentMapper接口的实现类 StudentMapper mapper = (StudentMapper) session.getMapper(StudentMapper.class); StudentEntity se = mapper.getStudent("123456"); //于是这个类就有了具体的getStudent方法 se.println(); List list=mapper.getStudentAll(); list.forEach((s)->{ s.println(); }); } }//End-Of-Main }

在Netbeans编译运行后的结果：

用JavaSE简单入门MyBatis连接MySQL…，javasemybatis

用JavaSE简单入门MyBatis连接MySQL…，javasemybatis

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