（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;
  }
  @Override
  public 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>

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​​