MyBatis入门（一）SqlSessionFactory

（1）新建数据库

 CREATE TABLE emp (
     id INT ( 10 ) PRIMARY KEY auto_increment,
     last_name VARCHAR(255),
     gender CHAR(1),
     email VARCHAR(255)
 )

（2）输入数据

INSERT INTO emp VALUES(1,"张三","男","we.com");

　　　　

（3）新建项目

　　　　

（4）导入Jar包

　　　　

（5）编写log4j

 <?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">
    <param name="Encoding" value="UTF-8" />
    <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="info" />
  </logger>
  <root>
    <level value="debug" />
    <appender-ref ref="STDOUT" />
  </root>
 </log4j:configuration>

（6）编写实体类

 public class Emp {

     private Integer id;
     private String lastName;
     private String geder;
     private String email;
     public Emp() {
         super();
     }
     public Emp(Integer id, String lastName, String geder, String email) {
         super();
         this.id = id;
         this.lastName = lastName;
         this.geder = geder;
         this.email = email;
     }
     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 getGeder() {
         return geder;
     }
     public void setGeder(String geder) {
         this.geder = geder;
     }
     public String getEmail() {
         return email;
     }
     public void setEmail(String email) {
         this.email = email;
     }
     @Override
     public String toString() {
         return "Emp [id=" + id + ", lastName=" + lastName + ", geder=" + geder + ", email=" + email + "]";
     }

（7）编写MyBatis的配置文件

 <?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/MyBatis"/>
         <property name="username" value="root"/>
         <property name="password" value="root"/>
       </dataSource>
     </environment>
   </environments>
   <mappers>
     <mapper resource="conf/EmpMapper.xml"/>
   </mappers>
 </configuration>

（8）编写Mapper文件EmpMapper.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="conf.EmpMapper">
   <select id="selectEmp" resultType="com.eu.pojo.Emp">
     select id,last_name lastName,gender,email from Emp where id = #{id}
   </select>
 </mapper>

（9）编写测试类

 　　@Test
     public  void testMapper() throws IOException {
         String resource = "conf/mybatis-config.xml";
         InputStream inputStream = Resources.getResourceAsStream(resource);
         SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

         SqlSession session = sqlSessionFactory.openSession();
         try {
           Emp emp = (Emp) session.selectOne("conf.EmpMapper.selectEmp", 1);
           System.out.println(emp);
         } finally {
           session.close();
         }
     }

（10）测试结果

 DEBUG 04-14 19:20:32,007 ==>  Preparing: select id,last_name lastName,gender,email from Emp where id = ?   (BaseJdbcLogger.java:145)
 DEBUG 04-14 19:20:32,073 ==> Parameters: 1(Integer)  (BaseJdbcLogger.java:145)
 DEBUG 04-14 19:20:32,107 <==      Total: 1  (BaseJdbcLogger.java:145)
 Emp [id=1, lastName=张三, geder=null, email=we.com]

这种方式还存在缺陷，

 Emp emp = (Emp) session.selectOne("conf.EmpMapper.selectEmp", 1);

如果传入一个字符呢？如何查？所以必须限制传入的是合法的数字。针对这种方式进行了修改，见下一篇  MyBatis入门（二）接口式编程