工具類 - 基于 Gson 的 JsonUtil 支援跨域

package com.util;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.gson.Gson;

public class JsonUtil {
	
	public JsonUtil(HttpServletRequest request,HttpServletResponse response){
		this.request = request;
		this.response = response;
	}

	/** 目前HttpServletRequest */
	protected HttpServletRequest request;
	/** 目前HttpServletResponse */
	protected HttpServletResponse response;
	
	protected PrintWriter writer;

	public PrintWriter getWriter() {
		try {
			writer = response.getWriter();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return writer ;
	}

	public void setWriter(PrintWriter writer) {
		this.writer = writer;
	}
	
	public HttpServletRequest getRequest() {
		return request;
	}

	public void setRequest(HttpServletRequest request) {
		this.request = request;
	}

	public HttpServletResponse getResponse() {
		return response;
	}

	public void setResponse(HttpServletResponse response) {
		this.response = response;
	}
	
	// JSON
	private void setJsonHeader(){
		HttpServletResponse response = getResponse();
		response.setContentType("application/json;charset=UTF-8");
		response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate");
		response.setHeader("Pragma", "no-cache");
		response.setDateHeader("Expires", 0);
		response.setHeader("Access-Control-Allow-Origin", "*");
		response.setHeader("Access-Control-Allow-Headers", "Authentication");
	}

	/**
	 * 警告：請不要直接使用此函數，防止産生緩存問題
	 * 請考慮使用outObjString
	**/
	public void outString(String str) {
		try {
			PrintWriter out = getResponse().getWriter();
			out.print(str);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	public void outObjString(Object obj, String code, String msg) {
		setJsonHeader();
		String jsonString =
				"{" +
				" \"code\": \"" + code + "\"," +
				" \"msg\": \"" + msg + "\", " +
				" \"data\": " + new Gson().toJson(obj) +
				"}";
		outString(jsonString);
	}
	
	public void outObjString(Object obj) {
		setJsonHeader();
		String jsonString = "{\"success\":true,\"data\":" + new Gson().toJson(obj) + "}";
		outString(jsonString);
	}

}
           

調用示例：

JsonUtil out = new JsonUtil(request, response);
out.outObjString(Object, "狀态碼", "狀态描述");