SpringBoot AsyncContext printWriter 推送数…

2018-11-27 08:31:19来源：博客园阅读 ()

做了一个功能，前端查看一些数据，而数据在后端是通过大量的分析比较得到了，时间比较长！假如得到这些数据（List<Object>）需要10分钟，所以现在只要后端得到一条数据 <Object>就直接推送到前端;

使用观察者模式，和 AsyncContext 异步处理

视图大概是这样

OK，如图所示贴上代码

1.被观察者

 1 import java.util.ArrayList;
 2 import java.util.List;
 3 import java.util.Observable;
 4 
 5 import org.apache.commons.lang3.StringUtils;
 6 
 7 import com.data2wisdom.res.dsmgr.common.StringUtil;
 8 
 9 public class ForginRelation extends Observable {
10     private int total;
11     private int stepNum; //比对到第N个
12     private String relationId;
13     private int status = 0;  //比对状态    0：初始化    ,  1 ：正在比对,  2：比对完成 , 3:异常
14     
15     private List<ForginRelationObj> ffos = new ArrayList<>();
16     
17     
18     
19     //这里是通知观察者
20     public void addOneFr(ForginRelationObj relationObj) {
21         System.out.println("执行了添加操作");
22         this.ffos.add(relationObj);
23         setChanged();
24         notifyObservers();
25     }
26

2，,观察者

 2 
 3 import java.io.IOException;
 4 import java.io.PrintWriter;
 5 import java.util.ArrayList;
 6 import java.util.List;
 7 import java.util.Observable;
 8 import java.util.Observer;
 9 
10 import javax.servlet.AsyncContext;
11 
12 import org.apache.log4j.Logger;
13 
14 import com.google.gson.Gson;
15 
16 public class FindRelationObserver implements Observer{
17     private static Logger log = Logger.getLogger(FindRelationObserver.class);
18     private AsyncContext  async;    
19     private int num ;
20     
21     public FindRelationObserver(AsyncContext  async,ForginRelation forginRelation) {
22         super();
23         this.async = async;
24         forginRelation.addObserver(this);//添加被观察者
25     }
26 
27     @Override
28     public void update(Observable fr, Object arg) {
29         try {
30             PrintWriter printWriter = null;
31             try {
32                 printWriter = async.getResponse().getWriter();
33             } catch (IOException e) {
34                 e.printStackTrace();
35                 log.info("异步获取数据异常:"+e);    
36             }
37         　　//业务逻辑可以不看
38             ForginRelation forginRelation = (ForginRelation)fr;
39             List<ForginRelationObj> ffos = forginRelation.getFfos();
40             List<ForginRelationObj> tempData = new ArrayList<>();
41             int temp = num;
42             num =  ffos.size();
43             for (int i = temp; i < num ; i++) {
44                 tempData.add(ffos.get(i));
45             }
46             Gson gson = new Gson();
47             String json = gson.toJson(tempData);
　　　　　　　　//这里是数据输出到前端， flush一下
48             printWriter.write("<script>  parent.dataRender('"+json+"'); </script>");  //parent中打开， 看最后面的页面请求方式
49             printWriter.flush();
50             
51             if(forginRelation.getStatus() == 2 || forginRelation.getStatus() == 3) {
52                 printWriter.close();
53                 forginRelation.deleteObserver(this);//异步结束，移除观察者
54                 async.complete();//异步结束
55             }
56         } catch (Exception e) {
57             
58             e.printStackTrace();
59         }
60     }
61 
62 }

3.请求接口

 1 @RequestMapping(value = "/result", method = { RequestMethod.GET })
 2     public void index(HttpServletResponse response,HttpServletRequest request,String relationId) {    
 3         response.setContentType("text/html;charset=UTF-8");
 4         response.setCharacterEncoding("UTF-8");
 5         AsyncContext async = null;
 6         PrintWriter writer = null;
 7         ForginRelation relation = null;
 8         
 9         try {
10             async = request.startAsync(request,response);
11             async.setTimeout(0);  //超时设置
34             relation = relationMap.getForginRelationById(relationId);
35             async.addListener(new ForginRelationAsyncListener());
36             async.start(new AsyncResult(async, relation)); //这里由于数据传递需要实现runnable 所以包装了个对象AsyncResult
39         }catch (Exception e) {
40         
41             e.printStackTrace();
42             logger.info(e);
43         
44         }finally {
45             
46         }

 1 import javax.servlet.AsyncContext;
 2 
 3 public class AsyncResult  implements Runnable{
 4     private AsyncContext  async;    
 5     
 6     private ForginRelation relation;
 7     
 8     public AsyncResult(AsyncContext async,ForginRelation relation){
 9         this.async = async;
10         this.relation = relation;
11     }
12 
13 
14     @Override
15     public void run() {
16         new FindRelationObserver(async, relation);
17     }

4.前端请求没理解，需要form表单请求不然会出问题，我也不理解啥原因

 1 <body>
 2 
 3     <div class="form-body layer-content">
 4 
 5         <div>
 6         
 7             <div style="padding:20px;">
 8                 <div class="form-group">
 9                 <!--     <h3 class="margin-bottom-10 sub">新增表</h3> -->
10                     <table class="layui-table" id="forginRelation"></table>
11                 </div>
12             </div>
13             
14         </div>
15         
16 
17     </div>
18 
19 
20     <div id="content" class="display_none" >
21         <form id="queryForm" name="queryForm" action="/rest/combing/findr/result" method="get">
22             <input type="text"  id="relationId" name="relationId" />
23         </form>
24     </div>
25 
26     <iframe id="dataCometFrame" src="" name="dataCometFrame" width="0" height="0" ></iframe>
　　　　 <script type="text/javascript">

　　　　　　$("#queryForm").attr("target", "dataCometFrame"); //需要在iframe中打开
　　　　　　$("#relationId").val($("base").attr("relationId")) //我的业务请求参数
　　　　　　$("#queryForm").submit();　　　　//提交表单

　　　　　　function dataRender(data){
　　　　　　　　console.log("dataRender:");
　　　　　　　　console.log(data);
　　　　　　}