个回答

• 慕粉231358792

  2017-06-01 22:11:17

  这个是传入到数据库的时候没有对数据进行编码，数据库读不到数据，jdbc:mysql://127.0.0.1:3306/micro_message?characterEncoding=utf8","root","root"

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• LebronJames_

  2016-07-27 20:09:32

  是空格的问题， sql.append(" and COMMAND =?");

  在and 的前面加一个空格。

  
  

  1

• 略坑

  2016-07-27 00:23:02

  package com.imooc.servlet;

  
  

  import java.io.IOException;

  import java.sql.Connection;

  import java.sql.DriverManager;

  import java.sql.PreparedStatement;

  import java.sql.ResultSet;

  import java.sql.SQLException;

  import java.util.ArrayList;

  import java.util.List;

  
  

  import javax.servlet.ServletException;

  import javax.servlet.http.HttpServlet;

  import javax.servlet.http.HttpServletRequest;

  import javax.servlet.http.HttpServletResponse;

  
  

  import com.imooc.bean.Message;

  
  

  /*

   *列表页面初始化控制 

   */

  @SuppressWarnings("serial")

  public class ListServlet extends HttpServlet {

  
  

  @Override

  protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {

  // TODO Auto-generated method stub

  try {

  req.setCharacterEncoding("UTF-8");

  String command=req.getParameter("command");

  String description=req.getParameter("description");

  Class.forName("com.mysql.jdbc.Driver");

   Connection conn= DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/micro_message","root","admin");

   StringBuilder sql=new StringBuilder();

   sql.append("select ID,COMMAND,DESCRIPTION,CONTENT from message where 1=1");

  List<String> paramlist=new ArrayList<String>();

   if(command!=null &&!"".equals(command.trim())){

   sql.append("and COMMAND =?");

   paramlist.add(command);

   }

   if(description!=null &&!"".equals(description.trim())){

   sql.append("and DESCRIPTION =?");

   paramlist.add(description);

   }

   PreparedStatement stat=conn.prepareStatement(sql.toString());

  for (int i=0;i<paramlist.size();i++) {

  stat.setString(i+1, paramlist.get(i));

  }

  ResultSet rs=stat.executeQuery();

  List <Message> messagelist=new ArrayList<Message>(); 

  System.out.println(sql);

  while(rs.next()){

  Message message=new Message();

     message.setId(rs.getString("ID"));

     message.setCommand(rs.getString("COMMAND"));

     message.setDescription(rs.getString("DESCRIPTION"));;

     message.setContent(rs.getString("CONTENT"));

  messagelist.add(message);

  }

           req.setAttribute("messagelist", messagelist);

  } catch (ClassNotFoundException e) {

  // TODO Auto-generated catch block

  e.printStackTrace();

  } catch (SQLException e) {

  // TODO Auto-generated catch block

  e.printStackTrace();

  }

  req.getRequestDispatcher("/WEB-INF/jsp/back/list.jsp").forward(req, res);

  }

  
  

  @Override

  protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {

  // TODO Auto-generated method stub

  doGet(req, res);

  }

  
  

  }

  
  

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