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) 
" />
   </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