（5）MyBatis小总结：一个简单的例子

日期：2017/12/6

       求职中，加紧学习。（引用自某位前辈）

     mybatis即是对JDBC的封装（重复代码的优秀封装），因为是半自动化ORM，所以sql其实需要我们自己写和封装的（xml标签装饰），下面介绍一个最简单的使用例子，实现“select * from employee where id=1”。

准备：

1. Mysql ，eclipse ；

2. jar包： mybatis-3.4.1.jar 、mysql-connector-java-5.1.37-bin.jar、log4j.jar（java常用开发包--log4j.jar ）

3. 目录结构:

|configuration.xml

|testcase.java

|User.java

|User.xml

4.代码

    4.1User.java：

package mybatis;public class User {private Integer id;private String lastName;private String email;private String gender;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getLastName() {return lastName;}public void setLastName(String lastName) {this.lastName = lastName;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}public String getGender() {return gender;}public void setGender(String gender) {this.gender = gender;}@Overridepublic String toString() {return "Employee [id=" + id + ", lastName=" + lastName + ", email="+ email + ", gender=" + gender + "]";}}

    4.2 configuration.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>    <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/test" />                <property name="username" value="root" />                <property name="password" value="" />            </dataSource>        </environment>    </environments>    <mappers>        <mapper resource="mybatis/User.xml" />    </mappers></configuration>

    4.3 User.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="User">    <select id="selectUser" resultType="mybatis.User">select * from employee where id=#{id}    </select></mapper>

 

    4.4 testcase.java：

package mybatis;import java.io.IOException;import java.io.Reader;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 testcase {public static void main(String[] args) throws IOException {        String resource = "mybatis/configuration.xml";          Reader reader = Resources.getResourceAsReader(resource);          SqlSessionFactory ssf = new SqlSessionFactoryBuilder().build(reader);          SqlSession session = ssf.openSession();          try {              User user = (User) session.selectOne("User.selectUser", "1");              System.out.println(user);          } catch (Exception e) {              e.printStackTrace();          } finally {              session.close();          } }}

测试结果：

log4j:WARN No appenders could be found for logger (org.apache.ibatis.logging.LogFactory).log4j:WARN Please initialize the log4j system properly.

Employee [id=1, lastName=mmb, email=[e-mail], gender=0]

测试可用。WHAT IS MORE :(6）MyBatis小总结：一个简单的例子--接口编程改进