如何在 Struts 2 中使用 JSP 返回 JSON 结果

问题描述

我知道在Struts2中可以使用json插件返回一个json类型的结果.json 也可以从 stream 结果返回，如 this 回答.

在 Ajax 结果的 Struts2 文档页面上JSP，我发现可以使用输出 JSON 的 JSP 返回 dispatcher 类型的结果.

<%@ 页面导入="java.util.Iterator,java.util.List,com.esolaria.dojoex.Book，com.esolaria.dojoex.BookManager"%><%String bookIdStr = request.getParameter("bookId");int bookId = (bookIdStr == null || "".equals(bookIdStr.trim()))?0 : Integer.parseInt(bookIdStr);Book book = BookManager.getBook(bookId);如果(书！= null){out.println(book.toJSONString());System.out.println("itis:" + book.toJSONString());}%>

但它使用 scriptlet 将 JSON 写入外部.我知道在 JSP 中使用 scriplets 是非常不鼓励的.但是我在这个问题中找不到我的问题的答案How can I Avoid Java code in JSP files, using JSP 2?.如何使用 JSP 结果生成 JSON 对象?有没有更好的方法从 JSP 返回 JSON 对象?

可以通过dispatcher结果返回一个JSP，然后使用<s:property/> 标记来调用将在 JSP 中返回序列化数据的操作方法.

您还应该为您的 JSP 表达正确的 contentType:

公共类 DispatcherJsonAction 扩展 ActionSupport {私人图书；@Action("dispatcherJson")@Result(name = ActionSupport.SUCCESS, location = "page.jsp")公共字符串执行(){book = loadBookSomeHow();返回成功；}公共字符串 getJsonBook(){Gson gson = 新 Gson();尝试 {返回 gson.toJson(book);} 捕捉(异常 e){返回 gson.toJson(e.getMessage());}}}

page.jsp:

<%@page language="java" contentType="application/json; charset=UTF-8" pageEncoding="UTF-8"%><%@taglib prefix="s" uri="/struts-tags" %><s:property value="jsonBook"/>

I know that in Struts2 can be used json plugin to return a json type result. A json could also be returned from the stream result like in this answer.

On the Struts2 docs page for Ajax result with JSP, I've found that it's possible to return dispatcher type result with JSP that outputs a JSON.

<%@ page import="java.util.Iterator,
         java.util.List,
         com.esolaria.dojoex.Book,
         com.esolaria.dojoex.BookManager" %>
<%
    String bookIdStr = request.getParameter("bookId");
    int bookId = (bookIdStr == null || "".equals(bookIdStr.trim())) 
        ? 0 : Integer.parseInt(bookIdStr);
    Book book = BookManager.getBook(bookId);
    if (book != null) {
        out.println(book.toJSONString());
        System.out.println("itis: " + book.toJSONString());
    }
%>

But it's using scriptlets to write JSON to the out. I know that using scriplets in JSP is highly discouraged. But I couldn't find the answer for my problem in this question How can I avoid Java code in JSP files, using JSP 2?. How can I use JSP result to generate a JSON object? Is there a better way to return JSON object from JSP?

You can return a JSP through the dispatcher result, then use <s:property /> tag to call an action method that will return the serialized data in the JSP.

You should also express the right contentType for your JSP:

public class DispatcherJsonAction extends ActionSupport {

    private Book book;

    @Action("dispatcherJson")
    @Result(name = ActionSupport.SUCCESS, location = "page.jsp")        
    public String execute(){
        book = loadBookSomeHow();
        return SUCCESS;
    }

    public String getJsonBook(){
        Gson gson = new Gson();
        try {
            return gson.toJson(book);
        } catch (Exception e){
            return gson.toJson(e.getMessage());
        }
    }

}

page.jsp:

<%@page language="java" contentType="application/json; charset=UTF-8" pageEncoding="UTF-8"%>
<%@taglib prefix="s" uri="/struts-tags" %>
<s:property value="jsonBook" />

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