request.getParameter（）在从另一个servlet调用java servlet时返回NULL [英] request.getParameter() returns NULL in java servlet on calling it from another servlet

问题描述

我创建了两个servlet Authenticate.java和Accept.java

以下是Authenticate.java的doGet函数

  PreparedStatement stmt = null; 
 PrintWriter out = response.getWriter（）; 
 
 response.setContentType（text / html）; 
 response.setCharacterEncoding（UTF-8）; 
尝试{
 int cnt = 0; 
 Class.forName（com.ibm.db2.jcc.DB2Driver）; 
 Connection con = DriverManager.getConnection（jdbc：db2：// localhost：50000 / SSMS，kiit，kiit）; 
 con.setAutoCommit（false）; 
 String s = request.getParameter（userName）; 
 if（s == null）{
 out.println（You Are Not Authorized）; 
 return; 
} 
 stmt = con.prepareStatement（SELECT COMP_ID，NAME，CONTACT FROM COMPANYREG）; 
 
 ResultSet rs = stmt.executeQuery（）; 
 while（rs.next（））{
 cnt ++; 
 out.println（< form action ='Accept'method ='post'>< input type ='text'size = '20'id ='cmpid'value ='+ rs.getString （1）+'>< br>名称：+ rs.getString（2）+< br>联系人：+ rs.getString（3）+< br>< input type =' submit'class ='confirm'id ='+ cnt +'value ='Approve'>< br>< / form>）; 
} 
  

和Heres Accept.java

  String user = request.getParameter（cmpid）; 
 
 PrintWriter out = response.getWriter（）; 
 response.setContentType（text / html）; 
 response.setCharacterEncoding（UTF-8）; 
 out.println（user =+ user）; 
尝试{
 String cid = null，pss = null，nam = null，add = null，sec = null，cnt = null，ema = null; 
 Class.forName（com.ibm.db2.jcc.DB2Driver）; 
 Connection con = DriverManager.getConnection（jdbc：db2：// localhost：50000 / SSMS，kiit，kiit）; 
 
 stmt = con.prepareStatement（SELECT * FROM COMPANYREG WHERE COMP_ID ='+ user +'）; 
 ResultSet rs = stmt.executeQuery（）; 
 out.println（query1）; 
 while（rs.next（））{
 out.println（query2）; 
 cid = rs.getString（1）; 
 pss = rs.getString（2）; 
 nam = rs.getString（3）; 
 add = rs.getString（4）; 
 sec = rs.getString（5）; 
 cnt = rs.getString（6）; 
 ema = rs.getString（7）; 
 
} 
 out.println（query3）; 
 stmt = con.prepareStatement（INSERT INTO COMPANY VALUES（'+ cid +'，'+ pss +'，'+ nam +'，'+ add +'，'+ sec +' ， + CNT +， ' + EMA +'））; 
 
 int numRowsChanged = stmt.executeUpdate（）; 
 if（numRowsChanged == 0）out.println（遇到一些错误请正确重新输入信息值）; 
 else out.println（您已成功注册，您的个人信息验证通过后将被允许登录。谢谢） 
  

在Accept.java类中，当我引用变量cmpid时，使用request.getParameter（cmpid ）;

它返回null ......有人可以告诉我究竟是什么问题吗？

解决方案

out.println（< form action ='Accept'method ='post'>< input type =' 'rs.getString（1）+'>< br>名称：+ rs.getString（2）+< br>联系人： + rs.getString（3）+< br>< input type ='submit'class ='confirm'id ='+ cnt +'value ='Approve'>< br>< / form> ;）;


将表单中的name属性添加为name = cmpid

I have made two servlets Authenticate.java and Accept.java

Here's the doGet function of Authenticate.java

      PreparedStatement stmt = null;
      PrintWriter out=response.getWriter();

      response.setContentType("text/html");  
      response.setCharacterEncoding("UTF-8");  
      try{
          int cnt=0;
          Class.forName("com.ibm.db2.jcc.DB2Driver");
          Connection con= DriverManager.getConnection("jdbc:db2://localhost:50000/SSMS", "kiit", "kiit");
          con.setAutoCommit(false);
          String s=request.getParameter("userName");
          if(s==null){
              out.println("You Are Not Authorized");
              return;
          }
          stmt=con.prepareStatement("SELECT COMP_ID,NAME,CONTACT FROM COMPANYREG");

          ResultSet rs=stmt.executeQuery();
          while(rs.next()){
              cnt++;
              out.println("<form action='Accept' method='post'> <input type='text'  size='20' id='cmpid' value='"+rs.getString(1)+"'><br> Name :"+rs.getString(2)+"<br>Contact: "+rs.getString(3)+"<br><input type='submit' class='confirm' id='"+cnt+"' value='Approve'><br></form>");
          }

And Heres Accept.java

               String user=request.getParameter("cmpid");

      PrintWriter out=response.getWriter();
      response.setContentType("text/html");  
      response.setCharacterEncoding("UTF-8"); 
      out.println("user = "+user);
      try{
          String cid = null,pss = null,nam = null,add = null,sec = null,cnt = null,ema = null;
          Class.forName("com.ibm.db2.jcc.DB2Driver");
          Connection con= DriverManager.getConnection("jdbc:db2://localhost:50000/SSMS", "kiit", "kiit");

          stmt=con.prepareStatement("SELECT * FROM COMPANYREG WHERE COMP_ID = '"+user+"'");
          ResultSet rs=stmt.executeQuery();
          out.println("query1");
          while(rs.next()){
              out.println("query2");
              cid = rs.getString(1);
              pss=rs.getString(2);
              nam=rs.getString(3);
              add=rs.getString(4);
              sec=rs.getString(5);
              cnt=rs.getString(6);
              ema=rs.getString(7);

          }
          out.println("query3");
          stmt=con.prepareStatement("INSERT INTO COMPANY VALUES ('"+cid+"','"+pss+"','"+nam+"','"+add+"','"+sec+"',"+cnt+",'"+ema+"')");

          int numRowsChanged= stmt.executeUpdate();
          if(numRowsChanged==0) out.println("Some Error Encountered Please Re-enter Information values Correctly");
          else out.println("You Were Registered Successfully.You will be allowed to login once your details are verified. Thank You");

In the Accept.java class when i refer to variable "cmpid" using request.getParameter("cmpid");

it is returning null ...... Can anybody tell me what actually is the problem here??

解决方案

out.println("<form action='Accept' method='post'> <input type='text'  size='20' id='cmpid' value='"+rs.getString(1)+"'><br> Name :"+rs.getString(2)+"<br>Contact: "+rs.getString(3)+"<br><input type='submit' class='confirm' id='"+cnt+"' value='Approve'><br></form>");

add name attribute in form as "name=cmpid"

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