java——mySQL数据库的增删改查实现

插入操作：

    //插入操作
    public static int add(String sql) {
        int i=0;
     
        DBConnection db = new DBConnection();
        try {        
            PreparedStatement preStmt = (PreparedStatement) db.conn.prepareStatement(sql);
            preStmt.executeUpdate();
            //Statement statement = (Statement) db.conn.createStatement();
            //statement.executeUpdate(sql);
            
            preStmt.close();
            db.close();//关闭连接 
            i = 1;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return i;//返回影响的行数，1为执行成功
    }

 查找操作：

//查找操作
    public static List< Map<String,String> > show(String sql, String[] params){
    	//params为想查询的列名数组  如
    	//public final static String [] USERNAME = {"id","username","password"};
    	
        // String sql ="select * from employee";
    	List< Map<String,String> > listmap = new ArrayList<>();
    	
         DBConnection db = new DBConnection();
         ResultSet rs = null;
         System.out.println("-----------------");
         System.out.println("姓名" +"\t"+ "邮箱" +"\t"+ "日期");
         System.out.println("-----------------");
         
         try {
            Statement stmt = (Statement) db.conn.createStatement();
            //rs是链表
            rs = (ResultSet) stmt.executeQuery(sql);
            while(rs.next()){
            	
            	Map<String,String> map = new HashMap<String,String>();
            	for(int i = 0; i < params.length; i++) {
            		
            		map.put(params[i], rs.getString(params[i]));
            	}
            	listmap.add(map);
            }
            rs.close();
            db.close();//关闭连接 
        } catch (SQLException e) {
            e.printStackTrace();
        }
		return listmap; 
     
    }

更新操作：

    //更新操作
    public static int update( String sql ) {
        int i =0;
       // String sql="update employee set email=?,pwd=? where name=?";
        DBConnection db = new DBConnection();
        
        try {
            PreparedStatement preStmt = (PreparedStatement) db.conn.prepareStatement(sql);
//            preStmt.setString(1, uemail);
//            preStmt.setString(2, upwd);
//            preStmt.setString(3, uname);
            preStmt.executeUpdate();
            
            preStmt.close();
            db.close();//关闭连接 
            i = 1;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return i;//返回影响的行数，1为执行成功
    }

删除操作：

    //删除操作
    public static int del(String sql) {
        int i=0;
      //  String sql="delete from employee where name=?";
        DBConnection db = new DBConnection();
        try {    
            PreparedStatement preStmt = (PreparedStatement) db.conn.prepareStatement(sql);
         
            preStmt.executeUpdate();
            
            preStmt.close();
            db.close();//关闭连接 
            
            i = 1;
        } catch (SQLException e){
            e.printStackTrace();
        }
        return i;//返回影响的行数，1为执行成功
    }