MyBatis的数据库操作入门（二）

àì夳堔傛蜴生んèń 2021-09-27 12:46 325阅读 0赞

前面写了个实体类，不过没有用到，下面我想打印smbms\_user表的所有信息

还是原来那个项目，在这里有个问题，比如你要食物，就要建造一次工厂（工厂是用完就摧毁）来生产，那这样就很麻烦了，每要一次食物就要建造一次工厂

下面我们可以把工厂封装起来，放到工具类util里面，以后要用到就调用就行了

新建一个包cn.bdqn.util，java名字为MyBatisUtil

package cn.bdqn.util;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    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 MyBatisUtil {
    	
    	
    	private static SqlSessionFactory sqlSessionFactory;
    	
    	/**
    	 * 创建SqlSessionFactory   只创建一次
    	 */
    	static{
    		try {
    			String resource = "mybatis-config.xml";
    			InputStream inputStream;
    			inputStream = Resources.getResourceAsStream(resource);
    			//创建SqlSessionFactory对象，读取配置文件
    			sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    		} catch (IOException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	
    	}
    	/**
    	 * 获得SqlSessionFactory
    	 * @return SqlSessionFactory
    	 */
    	public static SqlSessionFactory getSqlSessionFactory(){
    		
    		return sqlSessionFactory;
    		
    	}
    	/**
    	 * 获得 SqlSession
    	 * @return SqlSession
    	 */
    	public static SqlSession getSqlSession(){
    		return sqlSessionFactory.openSession(false);
    	}
    	/**
    	 * 关闭sqlSession
    	 * @param sqlSession
    	 */
    	public static void closeSession(SqlSession sqlSession){
    		if(sqlSession!=null){
    			sqlSession.close();
    		}
    	}
    	
    
    }

**静态代码块：**

在java中使用static关键字声明的代码块。静态块用于初始化类，为类的属性初始化。每个静态代码块只会执行一次。 由于JVM在加载类时会执行静态代码块，所以静态代码块先于主方法执行。  
**注意：**1 静态代码块不能存在于任何方法体内。2 静态代码块不能直接访问静态实例变量和实例方法，需要通过类的实例对象来访问。且只执行一次

然后在cn.bdqn.dao里面新建一个接口，名字要和映射文件一样

![70][]

![70 1][]

代码如下，用集合的形式

package cn.bdqn.dao;
    
    import java.util.List;
    
    import cn.bdqn.pojo.User;
    
    public interface UserMapper {
    
    	List<User> getUserList();
    }

cn.bdqn.dao里面的UserMapper.xml也要增加一个select代码

<?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="cn.bdqn.dao.UserMapper">
    
    	<select id="count" resultType="int"> 
    		Select count(1) from smbms_user
    	</select>
    	
    	<select id="getUserList" resultType="cn.bdqn.pojo.User">
    		Select * from smbms_user
    	</select>
    </mapper>

第一个select里面的在这里我们就没有用到，看第二个新增的select

id要和接口里面的方法名字一致，返回类型是实体类的路径，注意是.，sql语句的意思是查询这个表的详细信息

现在改写Test类，代码如下：

package cn.bdqn.test;
    
    
    import java.util.List;
    
    import org.apache.ibatis.session.SqlSession;
    import org.apache.log4j.Logger;
    
    import cn.bdqn.dao.UserMapper;
    import cn.bdqn.pojo.User;
    import cn.bdqn.util.MyBatisUtil;
    
    public class Test {
    
    	private static Logger logger = Logger.getLogger("Test");
    
    	public static void main(String[] args) {
    		
    		//getUserCount();
    		getUserList();
    	}
    	
    	public static void getUserList(){
    		SqlSession session = MyBatisUtil.getSqlSession();
    		//綁定Mapper接口
    		List<User> userList = session.getMapper(UserMapper.class).getUserList();
    		/*List<User> userList = session.getMapper(UserMapper.class).getUserList();*/
    		for (User user : userList) {
    			logger.debug("用户：" + user);
    		}
    		MyBatisUtil.closeSession(session);
    	}
    	
    
    /*	private static void getUserCount() {
    		SqlSession session = MyBatisUtil.getSqlSession();
    		// 调用mapper文件进行数据操作
    		int count = session.selectOne("cn.bdqn.dao.UserMapper.count");
    
    		logger.debug("用户数量是：" + count);
    		MyBatisUtil.closeSession(session);
    	}*/
    }

把上一个求记录数的代码封装了一下，因为没有使用，就注释掉了

运行了一下，结果如下：

\[DEBUG\] 2018-09-29 17:29:39,662 org.apache.ibatis.logging.LogFactory - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.  
\[DEBUG\] 2018-09-29 17:29:39,663 org.apache.ibatis.logging.LogFactory - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.  
\[DEBUG\] 2018-09-29 17:29:39,675 org.apache.ibatis.datasource.pooled.PooledDataSource - PooledDataSource forcefully closed/removed all connections.  
\[DEBUG\] 2018-09-29 17:29:39,675 org.apache.ibatis.datasource.pooled.PooledDataSource - PooledDataSource forcefully closed/removed all connections.  
\[DEBUG\] 2018-09-29 17:29:39,675 org.apache.ibatis.datasource.pooled.PooledDataSource - PooledDataSource forcefully closed/removed all connections.  
\[DEBUG\] 2018-09-29 17:29:39,675 org.apache.ibatis.datasource.pooled.PooledDataSource - PooledDataSource forcefully closed/removed all connections.  
\[DEBUG\] 2018-09-29 17:29:39,806 org.apache.ibatis.transaction.jdbc.JdbcTransaction - Opening JDBC Connection  
\[DEBUG\] 2018-09-29 17:29:40,131 org.apache.ibatis.datasource.pooled.PooledDataSource - Created connection 269468037.  
\[DEBUG\] 2018-09-29 17:29:40,132 cn.bdqn.dao.UserMapper.getUserList - ooo Using Connection \[com.mysql.jdbc.JDBC4Connection@100fc185\]  
\[DEBUG\] 2018-09-29 17:29:40,133 cn.bdqn.dao.UserMapper.getUserList - ==>  Preparing: Select \* from smbms\_user   
\[DEBUG\] 2018-09-29 17:29:40,153 cn.bdqn.dao.UserMapper.getUserList - ==> Parameters:   
\[DEBUG\] 2018-09-29 17:29:40,223 Test - 用户：User \[address=北京市海淀区成府路207号, birthday=Mon Oct 10 00:00:00 CST 1983, createdBy=1, creationDate=Thu Mar 21 16:52:07 CST 2013, gender=1, id=1, modifyBy=null, modifyDate=null, phone=13688889999, userCode=admin, userName=系统管理员, userPassword=1234567, userRole=1\]  
\[DEBUG\] 2018-09-29 17:29:40,223 Test - 用户：User \[address=北京市东城区前门东大街9号, birthday=Sat Dec 10 00:00:00 CST 1983, createdBy=1, creationDate=Fri Sep 28 22:58:39 CST 2018, gender=2, id=2, modifyBy=null, modifyDate=null, phone=13688884457, userCode=liming, userName=李明, userPassword=0000000, userRole=2\]  
\[DEBUG\] 2018-09-29 17:29:40,223 Test - 用户：User \[address=北京市朝阳区北辰中心12号, birthday=Tue Jun 05 00:00:00 CST 1984, createdBy=1, creationDate=Wed Dec 31 19:52:09 CST 2014, gender=2, id=5, modifyBy=null, modifyDate=null, phone=18567542321, userCode=hanlubiao, userName=韩路彪, userPassword=0000000, userRole=2\]  
\[DEBUG\] 2018-09-29 17:29:40,223 Test - 用户：User \[address=北京市海淀区学院路61号, birthday=Wed Jun 15 00:00:00 CST 1983, createdBy=1, creationDate=Mon Feb 11 10:51:17 CST 2013, gender=1, id=6, modifyBy=null, modifyDate=null, phone=13544561111, userCode=zhanghua, userName=张华, userPassword=0000000, userRole=3\]  
\[DEBUG\] 2018-09-29 17:29:40,223 Test - 用户：User \[address=北京市海淀区西二旗辉煌国际16层, birthday=Fri Dec 31 00:00:00 CST 1982, createdBy=1, creationDate=Wed Jun 11 19:09:07 CST 2014, gender=2, id=7, modifyBy=null, modifyDate=null, phone=13444561124, userCode=wangyang, userName=王洋, userPassword=0000000, userRole=3\]  
\[DEBUG\] 2018-09-29 17:29:40,223 Test - 用户：User \[address=北京市海淀区回龙观小区10号楼, birthday=Fri Mar 07 00:00:00 CST 1986, createdBy=1, creationDate=Thu Apr 21 13:54:07 CST 2016, gender=1, id=8, modifyBy=null, modifyDate=null, phone=18098764545, userCode=zhaoyan, userName=赵燕, userPassword=0000000, userRole=3\]  
\[DEBUG\] 2018-09-29 17:29:40,224 Test - 用户：User \[address=北京市朝阳区管庄新月小区12楼, birthday=Sun Jan 04 00:00:00 CST 1981, createdBy=1, creationDate=Wed May 06 10:52:07 CST 2015, gender=2, id=10, modifyBy=null, modifyDate=null, phone=13387676765, userCode=sunlei, userName=孙磊, userPassword=0000000, userRole=3\]  
\[DEBUG\] 2018-09-29 17:29:40,224 Test - 用户：User \[address=北京市朝阳区建国门南大街10号, birthday=Sun Mar 12 00:00:00 CST 1978, createdBy=1, creationDate=Wed Nov 09 16:51:17 CST 2016, gender=2, id=11, modifyBy=null, modifyDate=null, phone=13367890900, userCode=sunxing, userName=孙兴, userPassword=0000000, userRole=3\]  
\[DEBUG\] 2018-09-29 17:29:40,224 Test - 用户：User \[address=朝阳区管庄路口北柏林爱乐三期13号楼, birthday=Fri Mar 28 00:00:00 CST 1986, createdBy=1, creationDate=Tue Aug 09 05:52:37 CST 2016, gender=1, id=12, modifyBy=1, modifyDate=Thu Apr 14 14:15:36 CST 2016, phone=18098765434, userCode=zhangchen, userName=张晨, userPassword=0000000, userRole=3\]  
\[DEBUG\] 2018-09-29 17:29:40,224 Test - 用户：User \[address=北京市海淀区北航家属院10号楼, birthday=Wed Nov 04 00:00:00 CST 1981, createdBy=1, creationDate=Mon Jul 11 08:02:47 CST 2016, gender=2, id=13, modifyBy=null, modifyDate=null, phone=13689674534, userCode=dengchao, userName=邓超, userPassword=0000000, userRole=3\]  
\[DEBUG\] 2018-09-29 17:29:40,224 Test - 用户：User \[address=北京市朝阳区北苑家园茉莉园20号楼, birthday=Tue Jan 01 00:00:00 CST 1980, createdBy=1, creationDate=Sun Feb 01 03:52:07 CST 2015, gender=2, id=14, modifyBy=null, modifyDate=null, phone=13388886623, userCode=yangguo, userName=杨过, userPassword=0000000, userRole=3\]  
\[DEBUG\] 2018-09-29 17:29:40,224 Test - 用户：User \[address=北京市昌平区天通苑3区12号楼, birthday=Fri Dec 04 00:00:00 CST 1987, createdBy=1, creationDate=Sat Sep 12 12:02:12 CST 2015, gender=1, id=15, modifyBy=null, modifyDate=null, phone=18099897657, userCode=zhaomin, userName=赵敏, userPassword=0000000, userRole=2\]  
\[DEBUG\] 2018-09-29 17:29:40,224 org.apache.ibatis.transaction.jdbc.JdbcTransaction - Resetting autocommit to true on JDBC Connection \[com.mysql.jdbc.JDBC4Connection@100fc185\]  
\[DEBUG\] 2018-09-29 17:29:40,226 org.apache.ibatis.transaction.jdbc.JdbcTransaction - Closing JDBC Connection \[com.mysql.jdbc.JDBC4Connection@100fc185\]  
\[DEBUG\] 2018-09-29 17:29:40,227 org.apache.ibatis.datasource.pooled.PooledDataSource - Returned connection 269468037 to pool.

[70]: /images/20210923/2f8710af180744a78a4a0428663f6db2.png
[70 1]: /images/20210923/4ba21b85b1854de0babd3fe44c223977.png