<%@page import="java.sql.*"%>
<%@page import="servlet.DBConnect"%>
<% DBConnect db=new DBConnect();
ResultSet result=db.executeQuery("select * from mapdata");
%>然后,下面是DBConnect类代码
package servlet;
import java.sql.*;
public class DBConnect
{
public static final String driver="com.mysql.jdbc.Driver";
public static final String url="jdbc:mysql://localhost:3306/mydata";
public static final String user="root";
public static final String password="2224101360";
ResultSet resultset=null;
PreparedStatement statement=null;
Connection conn=null; public Connection getConnection()
{ try{Class.forName(driver);
return DriverManager.getConnection(url,user,password);
}
catch(ClassNotFoundException e){System.out.println("Driver not found");return null;}
catch(SQLException e){System.out.println("Error:"+e.getMessage());return null;}
} public ResultSet executeQuery(String sql) throws Exception
{
conn=this.getConnection();
statement=conn.prepareStatement(sql);
return resultset=statement.executeQuery();
}
public int executeUpdate(String sql)
{
try{
conn=this.getConnection();
statement=conn.prepareStatement(sql);
return statement.executeUpdate(); }catch(Exception e){System.out.println("Error:"+e.getMessage());return 0;}
}
public void closeAll() throws Exception
{
if(null!=resultset) resultset.close();
if(null!=statement) statement.close();
if(null!=conn) conn.close(); }
public DBConnect() {}jsp javajavajspservletmysql
<%@page import="servlet.DBConnect"%>
<% DBConnect db=new DBConnect();
ResultSet result=db.executeQuery("select * from mapdata");
%>然后,下面是DBConnect类代码
package servlet;
import java.sql.*;
public class DBConnect
{
public static final String driver="com.mysql.jdbc.Driver";
public static final String url="jdbc:mysql://localhost:3306/mydata";
public static final String user="root";
public static final String password="2224101360";
ResultSet resultset=null;
PreparedStatement statement=null;
Connection conn=null; public Connection getConnection()
{ try{Class.forName(driver);
return DriverManager.getConnection(url,user,password);
}
catch(ClassNotFoundException e){System.out.println("Driver not found");return null;}
catch(SQLException e){System.out.println("Error:"+e.getMessage());return null;}
} public ResultSet executeQuery(String sql) throws Exception
{
conn=this.getConnection();
statement=conn.prepareStatement(sql);
return resultset=statement.executeQuery();
}
public int executeUpdate(String sql)
{
try{
conn=this.getConnection();
statement=conn.prepareStatement(sql);
return statement.executeUpdate(); }catch(Exception e){System.out.println("Error:"+e.getMessage());return 0;}
}
public void closeAll() throws Exception
{
if(null!=resultset) resultset.close();
if(null!=statement) statement.close();
if(null!=conn) conn.close(); }
public DBConnect() {}jsp javajavajspservletmysql
16: <body>
17: <% DBConnect db=new DBConnect();
18: ResultSet result=db.executeQuery("select * from mapdata");
19: %>
20: <div id="allmap"></div>
21: </body>
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
root cause java.lang.NullPointerException
servlet.DBConnect.executeQuery(DBConnect.java:26)
org.apache.jsp.success_jsp._jspService(success_jsp.java:81)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.42 logs.
package servlet;
import java.sql.*;
public class DBConnect
{
public static final String driver="com.mysql.jdbc.Driver";
public static final String url="jdbc:mysql://localhost:3306/mydata";
public static final String user="root";
public static final String password="2224101360";
ResultSet resultset=null;
PreparedStatement statement=null;
Connection conn=null; public Connection getConnection()
{ try{Class.forName(driver);
return DriverManager.getConnection(url,user,password);
}
catch(ClassNotFoundException e){System.out.println("Driver not found");return null;}
catch(SQLException e){System.out.println("Error:"+e.getMessage());return null;}
} public ResultSet executeQuery(String sql) throws Exception
{
conn=this.getConnection();
statement=conn.prepareStatement(sql);
return resultset=statement.executeQuery();
}
public int executeUpdate(String sql)
{
try{
conn=this.getConnection();
statement=conn.prepareStatement(sql);
return statement.executeUpdate(); }catch(Exception e){System.out.println("Error:"+e.getMessage());return 0;}
}
public void closeAll() throws Exception
{
if(null!=resultset) resultset.close();
if(null!=statement) statement.close();
if(null!=conn) conn.close(); }
public DBConnect() {} public static void main(String[] args)
{
try{
servlet.DBConnect db=new servlet.DBConnect();
//int i=db.executeUpdate("insert into userinfo values (2,'wangqiang','123')");
//ResultSet result=db.executeQuery("select * from mapdata");
ResultSet result=db.doGetMapData();
System.out.println("-----------Result-------------");
System.out.println("username:"+"\t"+"password");
while(result.next())
{
System.out.println(result.getFloat("lng")+"\t"+result.getFloat("lat"));
}
}catch(Exception e) {System.out.println(e.getMessage());}
}
}
package servlet;
import java.sql.*;
public class DBConnect
{
public static final String driver="com.mysql.jdbc.Driver";
public static final String url="jdbc:mysql://localhost:3306/mydata";
public static final String user="root";
public static final String password="2224101360";
ResultSet resultset=null;
PreparedStatement statement=null;
Connection conn=null; public Connection getConnection()
{ try{Class.forName(driver);
return DriverManager.getConnection(url,user,password);
}
catch(ClassNotFoundException e){System.out.println("Driver not found");return null;}
catch(SQLException e){System.out.println("Error:"+e.getMessage());return null;}
} public ResultSet executeQuery(String sql) throws Exception
{
conn=this.getConnection();
statement=conn.prepareStatement(sql);
return resultset=statement.executeQuery();
}
public int executeUpdate(String sql)
{
try{
conn=this.getConnection();
statement=conn.prepareStatement(sql);
return statement.executeUpdate(); }catch(Exception e){System.out.println("Error:"+e.getMessage());return 0;}
}
public void closeAll() throws Exception
{
if(null!=resultset) resultset.close();
if(null!=statement) statement.close();
if(null!=conn) conn.close(); }
public DBConnect() {} public static void main(String[] args)
{
try{
servlet.DBConnect db=new servlet.DBConnect();
//int i=db.executeUpdate("insert into userinfo values (2,'wangqiang','123')");
ResultSet result=db.executeQuery("select * from mapdata");
System.out.println("-----------Result-------------");
System.out.println("username:"+"\t"+"password");
while(result.next())
{
System.out.println(result.getFloat("lng")+"\t"+result.getFloat("lat"));
}
}catch(Exception e) {System.out.println(e.getMessage());}
}}