java后端获取前端请求参数

纯servlet获取前端请求参数
测试页面

  <body><h2>输入帐号密码</h2><form action="test" method="post">帐号: <input type="text" name="username"/><br/>密码: <input type="text" name="password"/><br/><input type="submit" value="登录"/></form> </body>

 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{//方式一  Parameter的参数是我们提交表单的时候name的数值String username=request.getParameter("username");String password=request.getParameter("password");   System.out.println(username+"   "+password);System.out.println("==============");//获取所有参数Enumeration<String> parmNames1=request.getParameterNames();while (parmNames1.hasMoreElements()){String name = (String) parmNames1.nextElement();String value=request.getParameter(name);System.out.println(name+"=="+value);}System.out.println("==============");// 获取所有参数的map形式Map<String, String[]> map1=request.getParameterMap();//把map转换到EntrySetSet<Entry<String,String[]>> set1= map1.entrySet();//获取set的迭代器Iterator<Entry<String,String[]>> iterator1=set1.iterator();//遍历setfor (Entry<String, String[]> entry : set1){String name=entry.getKey();//value是一个数组,只取第一个,因为我们只有一个数值String value=entry.getValue()[0];System.out.println(name+"=="+value);}}

Controller：
package com.ysl.PassingParameters.controller;
import java.util.List;
import java.util.Map;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;import com.ysl.PassingParameters.bean.User;
import com.ysl.PassingParameters.dto.RetMsg;@Controller
public class TestController {/*** List<String>传参* @param listString* @return*/@RequestMapping("/listString")@ResponseBodypublic RetMsg listString(@RequestParam("listString[]") List<String> listString){System.out.println("listString:"+listString.toString());return RetMsg.success();}/*** List<User>传参* @param listUser* @return*/@RequestMapping("/listUsers")@ResponseBodypublic RetMsg listUsers(@RequestBody List<User> listUser){System.out.println("username:"+listUser.get(0).getUsername());return RetMsg.success();}/*** User[]传参* @param arrayUsers* @return*/@RequestMapping("/arrayUsers")@ResponseBodypublic RetMsg arrayUsers(@RequestBody User[] arrayUsers){System.out.println("username:"+arrayUsers[0].getUsername());return RetMsg.success();}/*** List<Map<String,Object>>传参* @param listMap* @return*/@RequestMapping("/listMap")@ResponseBodypublic RetMsg listMap(@RequestBody List<Map<String, String>> listMap){System.out.println("username:"+listMap.get(0).get("username"));return RetMsg.success();}/*** User对象传参* @param arrayUsers* @return*/@RequestMapping("/users")@ResponseBodypublic RetMsg users(@RequestBody User users){System.out.println("username:"+users.getUsername());System.out.println("username:"+users.getList().get(0).getUsername());return RetMsg.success();}
}
页面：
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>
<html>
<%application.setAttribute("path", request.getContextPath());%>
<head><script type="text/javascript" src="${path}/js/jquery.min.js"></script>
</head>
<body>
<h2>Hello World!</h2>
<button id="listString">List<String>传参</button>
<button id="listUser">List<User>传参</button>
<button id="arrayUsers">User[]传参</button>
<button id="listMap">List<Map<String,Object>>传参</button>
<button id="Users">User对象（属性包含List<User>）传参</button>
<script type="text/javascript">// List<String>传参$("#listString").click(function(){var idList = new Array();idList.push("1");idList.push("1");idList.push("1");$.ajax({type:"post",url:"${path}/listString",data:{"listString":idList},dataType:"json",success:function(retMsg){if(retMsg.code==200){alert("success");}else{alert("false");}}})})// List<User>传参$("#listUser").click(function(){var userList = new Array();userList.push({username: "zhangsan",password: "332"});userList.push({username: "zhangsan",password: "332"});$.ajax({type:"post",url:"${path}/listUsers",data:JSON.stringify(userList),dataType:"json",contentType : 'application/json;charset=utf-8', //设置请求头信息success:function(retMsg){if(retMsg.code==200){alert("success");}else{alert("false");}}})})//传User对象数组$("#arrayUsers").click(function(){var userList = [{username: "李四",password: "123"},{username: "张三",password: "332"}];$.ajax({type: "POST",url: "${path}/arrayUsers",data: JSON.stringify(userList),//将对象序列化成JSON字符串dataType:"json",contentType : 'application/json;charset=utf-8', //设置请求头信息success:function(retMsg){if(retMsg.code==200){alert("success");}else{alert("false");}}});})// List<Map<String,Object>>传参$("#listMap").click(function(){var userList = new Array();userList.push({username: "zhangsan",password: "332"});userList.push({username: "zhangsan",password: "332"});$.ajax({type:"post",url:"${path}/listMap",data:JSON.stringify(userList),dataType:"json",contentType : 'application/json;charset=utf-8', //设置请求头信息success:function(retMsg){if(retMsg.code==200){alert("success");}else{alert("false");}}})})//User对象传参$("#Users").click(function(){var list = new Array();list.push({username: "zhangsan",password: "332"});list.push({username: "zhangsan",password: "332"});var user = {};user.username = "张三";user.password = "密码";user.list = list;$.ajax({type:"post",url:"users",data:JSON.stringify(user),datatype:"json",contentType:"application/json;charset=utf-8",success:function(retMsg){if(retMsg.code==200){alert("success");}else{alert("false");}}})})
</script>
</body>
</html>

后端传值给前端

1，从Action中传值到JSP页面的方法

 ①在Action中定义一个成员变量，然后对这个成员变量提供get/set方法，在JSP页面就可以取到这个变量的值了。

1）在Action中定义成员变量

 //定义一个成员变量
private String message;//提供get/set方法
public String getMessage() {return message;
}
public void setMessage(String message) {this.message = message;
}

2）在JSP页面中取值

${message}

或者

<s:property value="message"/>

 ②使用一些Servlet API进行值的存取操作：HttpServletRequest、HttpSession和ServletContext。Struts2对这个三个对象用Map进行了封装，我们就可以使用Map对象来存取数据了。

1)在Action中存值

ActionContext actionContext = ActionContext.getContext();//get HttpServletRequest
Map<String,Object> request = (Map) actionContext.get("request");
request.put("a", "a is in request");//get HttpSession
//Map<String,Object> session = (Map) actionContext.get("session");
Map<String,Object> session = actionContext.getSession();
session.put("b", "b is in session");//get ServletContext
//Map<String,Object> application  = (Map) actionContext.get("application");
Map<String,Object> application  = actionContext.getApplication();
application.put("c", "c is in application");//get ServletActionContext.request
HttpServletRequest request=ServletActionContext.getRequest()
request.setAttribute("c2", "test5");
request.put("c3","test6")
//或者直接放入上下文中
ActionContext.getContext().put("d","d is in application");

2）在JSP页面上取值（使用EL表达式）

${a}
${b}
${c}
${d}
${c2}
${c3}or
${requestScope.a}
${sessionScope.b}
${applicationScope.c}
${actionContext.d}
${requestScope.c2}
${requestScope.c3}
or<%=request.getAttribute("d")%>  //使用ActionContext.getContext().put("d","d is an application")的情况

附加：ServletContext,ActionContext,ServletActionContext的区别

在ActionContext.getContext().put(“a”, " test3")后页面上用${a}或<s:property value=“#a”/>获得test3的值

#相当于ActionContext. getContext() ，#session.b表达式相当于ActionContext.getContext().getSession(). getAttribute(”b”)

③对于传递list的值，可以使用 actionContext的valueStack来传递值栈

1) 在后台使用Hibernate查询 ，EntityManager 通过createQuery()来getResultList()获得List，将list放入valueStack中
ActionContext.getContext().getValueStack().push(model);2)在页面上通过<s:iterator>标签遍历list的每条值显示在table上。

<table class="tablelist" >  <thead>  <tr>  <th width="100px;">编号</th>  <th>影片类型</th>  <th>影片名称</th>  <th>发布人</th>  <th>发布时间</th>  <th>审核状态</th>  <th>操作</th>  </tr>  </thead>  <tbody>  <s:iterator value="recordList" var="o" status="i">  <tr>  <td>${o.id}</td>  <td>${o.name }</td>  <td>${o.type}</td>  <td>${o.updateMember.memberName }</td>  </tr>  </s:iterator>  </tbody>  </table>

从前台向后台传递参数

①通过表单传递参数

 1)在前端jsp页面设置form表单，确定需要传递的参数name让用户在input中输入，通过点击按钮后submit()提交到后台

<s:form method="post" action="ActivityAction_toUI.action">  <table class="serTable">  <tbody>  <tr>  <td>  <label>活动名称</label>  </td>  <td>  <input type="text" class="serput" name="activityName" placeholder="输入文本"/>  </td>  <td>  <s:submit cssClass="btn1" value="搜索" onclick="submit();" />  </td>  </tr>  </tbody>  </table>  </s:form>

2)点击搜索后activityName会放到HttpServletRequest 中

HttpServletRequest httpReq = ServletActionContext.getRequest()；
String s = httpReq.getParameter("activityName");

另外，在后台也可以通过extends ActionSupport 并构建get/set方法在后台获得其值

        private String activityName;  public String getActivityName() {  return activityName;  }  public void setActivityName(String activityName) {  this.activityName = activityName;  }  public String list(){  System.out.println(activityName);  }

②通过超链接传递参数

 1)前台通过超链接跳转时将参数加到方法的后面

<s:a cssClass="acolor" target="mainBody" theme="simple"  action="ActivityAction_info.action?Id=%{Id}&pageNum=%{pageNum}&infot=\"mylittlepony\"" ><imgsrc="${pageContext.request.contextPath}/images/info.png"title="查看" /></s:a>

2)后台通过HttpServletRequest 获得超链接后面参数所对应的值

HttpServletRequest httpReq = ServletActionContext.getRequest()；
<pre name="code" class="java">Long id= Long.parseLong(httpReq.getParameter("Id"));