idea上MyBatis第一个例子

接着上面创建的maven项目来。

1.java目录下创建cn.happy.entity包

2.idea下创建数据库连接

配置连接参数

3.把数据库表变成实体类

导入成功，改一下包名就可以用了

4.新建cn.happy.dao包，在下面新建IUserDAO接口，代码如下

 package cn.happy.dao;

 import cn.happy.entity.Smbms_user;

 import java.util.List;

 public interface IUserDAO {
     List<Smbms_user> findAll();
 }

5.在IUserDAO同包下新建IUserDAO.xml文件（俗称小配置），文件名一定要相同（这样做可以规避后面的一些问题）。

官方文档中找到

2.1.4 Exploring Mapped SQL Statements

把下面的文档直接粘贴到IUserDAO.xml里

 <?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="org.mybatis.example.BlogMapper">
  <select id="selectBlog" parameterType="int" resultType="Blog">
  select * from Blog where id = #{id}
  </select>
 </mapper>

修改包名和<mapper>节点，比如我的代码修改如下即可

 <?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">
 <!--关联接口的全限定名-->
 <mapper namespace="cn.happy.dao.IUserDAO">
     <!--大配置中settings autoMappingBehavior NONE,所以数据库只会装配以下column-->
     <resultMap id="UserMapper" type="cn.happy.entity.Smbms_user">
         <id property="id" column="id"/>
         <result property="username" column="username"/>
         <result property="userpassword" column="userpassword"/>
     </resultMap>
     <!--id要与接口中的方法名相同-->
     <select id="findAll" resultMap="UserMapper">
         select * from smbms_user
     </select>
 </mapper>

6.配置resources

这里需要配置三个文件

1.jdbc.properties

2.log4j.properties

3.mybatis-config.xml

jdbc.properties

 jdbc.driver=com.mysql.jdbc.Driver
 jdbc.url=jdbc:mysql:///t14_smbms?characterEncoding=utf8&useSSL=true
 jdbc.username=root
 jdbc.password=root

log4j.properties

 log4j.rootLogger=debug,stdout,file
 ### direct log messages to stdout ###
 log4j.appender.stdout=org.apache.log4j.ConsoleAppender
 log4j.appender.stdout.Target=System.out
 log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
 log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{}:%L - %m%n

 ### direct messages to file mylog.log ###
 log4j.appender.file=org.apache.log4j.FileAppender
 log4j.appender.file.File=c:\\logs\\log.log
 log4j.appender.file.layout=org.apache.log4j.PatternLayout
 log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{}:%L - %m%n

 ### set log levels - for more verbose logging change 'info' to 'debug' ###

 log4j.logger.cn.happy.dao=debug, stdout,file

mybatis-config.xml,俗称大配置

 <?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>
     <!--引入 jdbc.properties-->
     <properties resource="jdbc.properties"/>
     <settings>
         <setting name="logImpl" value="LOG4J"/>
         <setting name="autoMappingBehavior" value="NONE"/>
     </settings>
     <!--别名，这里不使用别名，一律使用全限定名-->
     <!--<typeAliases>
         <package name="cn.happy.entity"/>
     </typeAliases>-->
     <!--DB connection info,配置mybatis多套运行环境-->
     <environments default="development">
         <environment id="development">
             <!--采用jdbc事务管理-->
             <transactionManager type="JDBC"/>
             <dataSource type="POOLED">
                 <property name="driver" value="${jdbc.driver}"/>
                 <property name="url" value="${jdbc.url}"/>
                 <property name="username" value="${jdbc.username}"/>
                 <property name="password" value="${jdbc.password}"/>
             </dataSource>
         </environment>
     </environments>
     <!--大配置关联小配置-->
     <mappers>
         <!--关联单个小配置,不能重复关联-->
         <mapper resource="cn/happy/dao/IUserDAO.xml"/>
         <!--关联整个包,dao层接口名字和对应的xml名字要一样-->
         <!--<package name="cn.happy.dao"/>-->
     </mappers>
 </configuration>

7.编写MyBatisUtil类

 package cn.happy.util;

 import org.apache.ibatis.io.Resources;
 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;
 import org.apache.ibatis.session.SqlSessionFactoryBuilder;

 import java.io.IOException;
 import java.io.InputStream;

 public class MyBatisUtil {
     private static InputStream is;
     private static SqlSessionFactory sqlSessionFactory;
     static {
         try {
             is=Resources.getResourceAsStream("mybatis-config.xml");
         } catch (IOException e) {
             e.printStackTrace();
         }
         sqlSessionFactory= new SqlSessionFactoryBuilder().build(is);
     }
     private MyBatisUtil(){}
     public static SqlSession getSession(){
         return sqlSessionFactory.openSession();
     }
 }

8.创建测试类

代码：

 package cn.happy.test;

 import cn.happy.dao.IUserDAO;
 import cn.happy.entity.Smbms_user;
 import cn.happy.util.MyBatisUtil;
 import org.apache.ibatis.session.SqlSession;
 import org.junit.Test;

 import java.util.List;

 public class Test20170916 {
     @Test
     public void findAll(){
         SqlSession session = MyBatisUtil.getSession();
         IUserDAO mapper = session.getMapper(IUserDAO.class);
         List<Smbms_user> users = mapper.findAll();
         for (Smbms_user user:users
              ) {
             System.out.println(user.getId()+"\t"+user.getUsername()+"\t"+user.getUserpassword());
         }
     }
 }

运行结果：