JDBCUtils工具类

开发步骤:

  1.私有化构造函数,外界无法直接创建对象;

  2.提供公共的,静态的,getConnection方法,用来给外界提供数据库连接;

  3.提供公共的,静态的,close方法,用来释放资源

JDBCUtils.java

package cn.yikuan.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;
/**
 * 这个类用来提供JDBC的工具类
 * @author Administrator
 *
 */
public class JDBCUtils {
    //1.私有化构造函数,外界无法直接创建对象
    private JDBCUtils(){

    }

    static ResourceBundle rb = null;
    static {
        //读取属性文件
        rb = ResourceBundle.getBundle("jdbc");
    }

    //2.提供公共的,静态的,getConnection方法,用来给外界提供数据库连接
    public static Connection getConnection(){
        try {
            //2.1注册驱动
            Class.forName(rb.getString("driverClass"));
            //2.2获取数据库连接
            String url = rb.getString("jdbcUrl");
            String user = rb.getString("user");
            String password = rb.getString("password");
            Connection conn = DriverManager.getConnection(url, user, password);
            return conn;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;    
    }

    //3.提供公共的,静态的,close方法,用来释放资源
    public static void close(ResultSet rs,Statement st,Connection conn){
        //3.1非空判断,防止空指针异常
        //3.2手动置为空,保证完全释放
        if(rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                rs = null;
            }
        }
        if(st != null){
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                st = null;
            }
        }
        if(conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                conn = null;
            }
        }
    }
}

 

TestUtils.java

package cn.yikuan.test;
/**
 * 这个类用来测试工具类
 */
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import org.junit.Test;
import cn.tedu.util.JDBCUtils;

public class TestUtils {
    @Test
    public void hello(){
        Connection conn = null;
        Statement st = null;
        ResultSet rs = null;
        try {
            //1.注册驱动;//2.获取数据库连接 java.sql.Connection;
            conn = JDBCUtils.getConnection();
            //3.获取传输器
            st = conn.createStatement();
            //4.执行sql
            String sql = "select * from user";
            rs = st.executeQuery(sql);
            //5.遍历结果集
            while(rs.next()){
                String id = rs.getString(1);
                //String id = rs.getString("id");
                String username = rs.getString(2);
                String password = rs.getString(3);
                System.out.println(id+username+password);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.close(rs, st, conn);
        }    
    }
}

 

posted @ 2018-08-22 18:51  yikuandyk  阅读(1793)  评论(0编辑  收藏  举报