模仿QueryRunner的底层实现

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package cn.xiechengxu.dbutils;import javax.sql.DataSource;import java.sql.*;/** * Created by zhangqiang on 17/6/23. */public class MyQueryRunner {    private DataSource ds;    public MyQueryRunner() {    }    public MyQueryRunner(DataSource ds){        this.ds=ds;    }    public <T> T query(Connection con,String sql ,MyResultSetHandler<T> mrs, Object ...params) throws SQLException {        PreparedStatement pst=con.prepareStatement(sql);        ParameterMetaData pmd=pst.getParameterMetaData();        int count=pmd.getParameterCount();        for(int i=1;i<=count;i++){            pst.setObject(i,params[i-1]);        }        ResultSet rs=pst.executeQuery();//得到结果集，要将结果集封装成用户想要的对象，但是，工具不知道用户需求        return mrs.handle(rs);    }    public int update(Connection con,String sql , Object ...params) throws SQLException {        PreparedStatement pst=con.prepareStatement(sql);        ParameterMetaData pmd=pst.getParameterMetaData();        int count=pmd.getParameterCount();        for(int i=1;i<=count;i++){            pst.setObject(i,params[i-1]);        }        int row= pst.executeUpdate();        //关闭资源        pst.close();        return row;    }    public int update(String sql , Object ...params) throws SQLException {        Connection con=ds.getConnection();        PreparedStatement pst=con.prepareStatement(sql);        ParameterMetaData pmd=pst.getParameterMetaData();        int count=pmd.getParameterCount();        for(int i=1;i<=count;i++){            pst.setObject(i,params[i-1]);        }        int row= pst.executeUpdate();        //关闭资源        pst.close();        con.close();        return row;    }}

package cn.xiechengxu.dbutils.domain;import cn.xiechengxu.dbutils.MyQueryRunner;import cn.xiechengxu.dbutils.MyResultSetHandler;import cn.xiechengxu.utils.DataSourceUtils;import org.junit.Test;import java.sql.ResultSet;import java.sql.SQLException;/** * Created by zhangqiang on 17/6/23. */public class MyQueryRunnerTest {    @Test    public void updateTest() throws SQLException{        String sql="delete from account where id=?";        MyQueryRunner mqr=new MyQueryRunner();        mqr.update(DataSourceUtils.getConnection(),sql,3);    }    @Test    public void selectTest() throws SQLException {        String sql="select * from account where id=?";        MyQueryRunner mqr=new MyQueryRunner();       Account a=mqr.query(DataSourceUtils.getConnection(), sql, new MyResultSetHandler<Account>() {            @Override            public Account handle(ResultSet rs) throws SQLException {                Account a=null;                if(rs.next()){                    a=new Account();                    a.setId(rs.getInt("id"));                    a.setName(rs.getString("name"));                    a.setMoney(rs.getDouble("money"));                }                return a;            }        }, 2);       System.out.print(a);    }}

public interface MyResultSetHandler<T> {    public T handle(ResultSet rs)throws SQLException;}

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