mybatis之CRUD

﹏ヽ暗。殇╰゛Y 2023-07-03 10:46 77阅读 0赞

##### CRUD #####

要进行crud操作，首先得有一张表，与之对应的应该有一个实体类，简单的做单表的CRUD，因此建立一个实体类

package mybatis2020001.model;
    
    import java.io.Serializable;
    
    public class account implements Serializable{
        
    
    	/**
    	 * 
    	 */
    	private static final long serialVersionUID = 1L;
    	
    	private int id;
    	private String name;
    	private double money;
    	public int getId() {
        
    		return id;
    	}
    	public void setId(int id) {
        
    		this.id = id;
    	}
    	public String getName() {
        
    		return name;
    	}
    	public void setName(String name) {
        
    		this.name = name;
    	}
    	public double getMoney() {
        
    		return money;
    	}
    	public void setMoney(int money) {
        
    		this.money = money;
    	}
    	@Override
    	public String toString() {
        
    		return "account [id=" + id + ", name=" + name + ", money=" + money + "]";
    	}
    	
    }

现在，需要使用mybatis建立实体类与表之间的映射关系  
因此，需要建立一个映射关系文件：

<?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="com.baidu.mybatis2020001.mappers">
      <select id="selectacc" resultType="account" >
        select * from account where id = #{
        id}
      </select>
      <insert id="addaccount" parameterType="account" keyProperty="id">
      INSERT INTO account (name,money)VALUES(#{
        name},#{
        money})
      </insert>
      
      <update id="updateacc" parameterType="account">
      UPDATE account SET NAME=#{
        name},money=#{
        money} WHERE id=#{
        id};
      </update>
      
      <delete id="deleteacc">
      DELETE FROM account WHERE id=#{
        id}
      </delete>
      
      <select id="selectAll" resultType="account">
      select * from account
      </select>
    </mapper>

我们想要让这个操作执行起来，那么必须拿到session对象，

static {
        
    
    		try {
        
    			input = Resources.getResourceAsStream(RESOURCE);
    
    			sqlsessionfactory = new SqlSessionFactoryBuilder().build(input);
    
    		} catch (Exception e) {
        
    			e.printStackTrace();
    		} finally {
        
    
    			if (input != null) {
        
    				try {
        
    					input.close();
    				} catch (IOException e) {
        
    					e.printStackTrace();
    				}
    			}
    
    		}
    
    	}

在这里我们获取到了sqlsessionfactory ，将这个写在工具类中一遍共用，而不能直接将sqlsession进行直接获取，因为sqlsession不是安全的，是谁在调用就使用谁的sqlsession。这里的sqlsessionfactory 获取使用了工厂模式进行构建，接下来就是进行具体的操作：

package mybatis2020001.dao;
    
    import org.apache.ibatis.session.SqlSessionFactory;
    
    import java.util.List;
    
    import org.apache.ibatis.session.SqlSession;
    import org.apache.log4j.Logger;
    
    
    import mybatis2020001.model.account;
    import mybatis2020001.utils.DBUtils;
    
    public class accountDao {
        
    	
    	private SqlSessionFactory sqlsessionfactory=DBUtils.getSqlSessionFactory("");
    	
    	private static Logger log=Logger.getLogger(accountDao.class);
    	
    	public account queryAccount(int id) {
        
    		account acc=null;
    		SqlSession session=null;
    		try {
        
    			session=sqlsessionfactory.openSession();
    			acc=session.selectOne("com.baidu.mybatis2020001.mappers.selectacc",id);
    		}catch(Exception e) {
        
    			log.error(e);
    		}finally {
        
    			if(session!=null) {
        
    				session.close();
    			}
    		}
    		return acc;
    		
    	}
    	public int addaccount(account acc) {
        
    		int i=0;
    		SqlSession session=null;
    		try {
        
    			session=sqlsessionfactory.openSession();
    			session.insert("com.baidu.mybatis2020001.mappers.addaccount",acc);
    			i=acc.getId();
    			session.commit();
    		}catch(Exception e) {
        
    			session.rollback();
    			log.error(e);
    		}finally {
        
    			if(session!=null) {
        
    				session.close();
    			}
    		}
    		return i;
    		
    	}
    	public int updateacc(account acc) {
        
    		int i=0;
    		SqlSession session=null;
    		try {
        
    			session=sqlsessionfactory.openSession();
    			i=session.update("com.baidu.mybatis2020001.mappers.updateacc", acc);
    			session.commit();
    		}catch(Exception e) {
        
    			session.rollback();
    			log.error(e);
    		}finally {
        
    			if(session!=null) {
        
    				session.close();
    			}
    		}
    		return i;
    	}
    	public int deleteacc(int id) {
        
    		int i=0;
    		SqlSession session=null;
    		try {
        
    			session=sqlsessionfactory.openSession();
    			i=session.delete("com.baidu.mybatis2020001.mappers.deleteacc", id);
    			session.commit();
    		}catch(Exception e) {
        
    			session.rollback();
    			log.error(e);
    		}finally {
        
    			if(session!=null) {
        
    				session.close();
    			}
    		}
    		return i;
    	}
    	
    	public List<account> queryAcc(){
        
    		List<account> list=null;
    		SqlSession session=null;
    		try {
        
    			session=sqlsessionfactory.openSession();
    			list=session.selectList("com.baidu.mybatis2020001.mappers.selectAll");
    		}catch(Exception e) {
        
    			log.error(e);
    		}finally {
        
    			if(session!=null) {
        
    				session.close();
    			}
    		}
    		return list;
    	}
    	
    }

在这个过程中要注意事物，mybatis默认事物是关闭的，我们要将事物开启，否则执行不报错，但是对于除了查之外的操作数据库并不持久化。