JavaWeb开发基础：连接数据库的demo和数据库连接工具类DB.java

JavaWeb开发基础：连接数据库的demo和数据库连接工具类DB.java

 

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
public class ShowRs extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request,
                         HttpServletResponse response) throws ServletException, IOException {

        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;

        response.setContentType("text/html");
        //输出编码是gb2312
        response.setCharacterEncoding("gb2312");
        PrintWriter out = response.getWriter();

        out.println("");
        out.println("");
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost/blog?user=root&password=");
            stmt = conn.createStatement();
            rs = stmt.executeQuery("select * from blogs");
            while(rs.next()){
                out.println("");
                out.println("");
                out.println("");
            }
            out.println("
Content:
" + rs.getString("username") + "
");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if(rs != null) {
                    rs.close();
                    rs = null;
                }
                if(stmt != null) {
                    stmt.close();
                    stmt= null;
                }
                if(conn != null) {
                    conn.close();
                    conn = null;
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

}

import java.sql.*;
public class DB {
    //驱动名字
    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://localhost:3306/blog";
    static final String USER = "root";
    static final String PASS = "";

    static {
        try {
            //反射
            Class.forName(JDBC_DRIVER);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() throws SQLException {
        return DriverManager
                .getConnection(DB_URL, USER,PASS);
    }

    public static void closeAll(Connection conn,Statement stmt,ResultSet rs) throws SQLException {
        if(rs!=null) {
            rs.close();
        }
        if(stmt!=null) {
            stmt.close();
        }
        if(conn!=null) {
            conn.close();
        }
    }
    public int executeSQL(String preparedSql, Object[] param) throws ClassNotFoundException {
        Connection conn = null;
        PreparedStatement pstmt = null;
        /* 处理SQL,执行SQL */
        try {
            //得到数据库连接
            conn = getConnection();
            //得到PreparedStatement对象
            pstmt = conn.prepareStatement(preparedSql);
            if (param != null) {
                for (int i = 0; i < param.length; i++) {
                    //为预编译sql设置参数
                    pstmt.setObject(i + 1, param[i]);
                }
            }
            //执行SQL语句
            ResultSet num = pstmt.executeQuery();
        } catch (SQLException e) {
            //处理SQLException异常
            e.printStackTrace();
        } finally {
            try {
                DB.closeAll(conn, pstmt, null);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return 0;
    }

}

补充一个马士兵写的DB工具类：

import java.sql.*;
 
public class DB {
	public static Connection getConn() {
		Connection conn = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection("jdbc:mysql://localhost/bbs?user=root&password=root");
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
		return conn;
	}
	
	public static Statement getStatement(Connection conn) {
		Statement stmt = null; 
		try {
			if(conn != null) {
				stmt = conn.createStatement();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return stmt;
	}
	
	public static ResultSet getResultSet(Statement stmt, String sql) {
		ResultSet rs = null;
		try {
			if(stmt != null) {
				rs = stmt.executeQuery(sql);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return rs;
	}
	
	public static void closeConn(Connection conn) {
		try {
			if(conn != null) {
				conn.close();
				conn = null;
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	public static void closeStmt(Statement stmt) {
		try {
			if(stmt != null) {
				stmt.close();
				stmt = null;
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	public static void closeRs(ResultSet rs) {
		try {
			if(rs != null) {
				rs.close();
				rs = null;
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
}