在servlet和jsp中處理web表單數據

1.String s = (String)request.getParameter("name");
2.String[] args = (String[])request.getParameterValues("name");  //獲得多值
3.通過迭代的getParameterMap方式獲得值
/*Map param_map = request.getParameterMap();
if(param_map == null){
 throw new ServletException("param_map is null");
}
Iterator iterator = param_map.entrySet().iterator();
while(iterator.hasNext()){
 Map.Entry me = (Map.Entry)iterator.next();
 out.print(me.getKey()+":");
 String[] args = (String[])me.getValue();
 for(int i = 0 ; i < args.length ; i++){   //處理多值
  out.print(args[i]);
 }
 out.print("<br>");
}*/
4.通過 getParameterNames 來迭代獲得值
/*Enumeration enumeration = request.getParameterNames();
while(enumeration.hasMoreElements()){
 String key = (String)enumeration.nextElement();
 String[] values = request.getParameterValues(key);
    out.print(key+" : ");
 for( int i = 0 ; i < values.length ; i++ ){
 out.print(values[i]);
 if(i < values.length - 1)
  out.print(",");
    }
 out.print("<br>");
}
*/

在servlet中，如果要訪問該servlet的配置參數，或者該servlet的相關信息，可以用
this.getServletConfig() 獲得這個對象
this.getServletContext() 能獲得整個上下文的信息

在servlet中，如果有新的轉發
RequestDispatcher dispatcher  = request.getRequestDispatcher("/PrintLogInfo?man=leishiran");
dispatcher.forward(request,response);
那么在新的接收servlet中，仍然響應表單提交的方法

使用過濾起讀取參數值
創建filter的類
package testfilterservlet;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class MyFirstFilter implements Filter {

 private FilterConfig config;

 public void init(FilterConfig filterConfig) throws ServletException {
  // TODO 自動生成方法存根
  this.config = filterConfig;
  System.out.println("MyFirstFilter init!");
 }
 public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {
  // TODO 自動生成方法存根
  
  String myName = (String)request.getParameter("name");
  if(myName.equals("lsr")){
   System.out.print("lsr");
   chain.doFilter(request,response); //繼續響應下一個filter或者servlet
  }else{
   System.out.print("not lsr");
   RequestDispatcher dispatcher = request.getRequestDispatcher("/testForm/testform1.html");
   dispatcher.forward(request,response);
  }
 }
 public void destroy() {
  // TODO 自動生成方法存根
  
  System.out.println("MyFirstFilter destroy!");
 }
}

然后注冊(簡寫)
<web-app>
        <filter>
  <filter-name>MyFirstFilter</filter-name>
  <filter-class>testfilterservlet.MyFirstFilter</filter-class>
 </filter>
 <filter-mapping>
  <filter-name>MyFirstFilter</filter-name>
  <servlet-name>PrintLog</servlet-name> //這里可以使用 url-pattern
 </filter-mapping>

 <servlet>
  <description></description>
  <display-name>PrintLog</display-name>
  <servlet-name>PrintLog</servlet-name>
  <servlet-class>testservlet.PrintLog</servlet-class>
  <init-param>
   <param-name>des</param-name>
   <param-value>this is a test</param-value>
  </init-param>
 </servlet>
 <servlet-mapping>
  <servlet-name>PrintLog</servlet-name>
  <url-pattern>/PrintLog</url-pattern>
 </servlet-mapping>
</web-app>

學的這里，覺得在這樣的結構下開發項目貌似很爽，只需要在xml進行注冊，而源文件不用做任何修改，就可以添加新的功能！