[英]Dispaly image through servlet on jsp
從Servlet中,我生成JPEG圖像並寫入該Servlet的輸出流中。通過jsp,我調用此Servlet URL並將圖像顯示為類似於帶有照片的用戶個人資料。 這里的問題是,第一次登錄時,它將動態生成圖像並顯示,但是下次,如果我先關閉瀏覽器登錄,它將顯示privies圖片,然后將顯示當前圖片。
JSP:
<div class="sortable">
<div class="box span5" style="margin-left: 50px;">
<div class="box-header well">
<h2><i class="icon-th"></i>Employee Attendance</h2>
<div class="box-icon">
<a href="#" class="btn btn-minimize btn-round"><i class="icon-chevron-up"></i></a>
</div>
</div>
<div class="box-content" style="height:230px;" >
<img border="0" src="admissionenquirylist.do?method=image" alt="Pulpit rock" width="370" height="240"/>
</div>
</div>
</div>
Servlet:
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package com.treamis.admission.process;
import com.google.gson.Gson;
import com.treamis.entity.Academicyearmaster;
import com.treamis.entity.AdmissionenquiryStudentdetails;
import com.treamis.entity.EmployeeEntity;
import com.treamis.hr.employee.PaginationClass;
import com.treamis.hr.employee.SetPaginationRecords;
import java.io.OutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.actions.LookupDispatchAction;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionForward;
import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import javax.servlet.ServletOutputStream;
/**
*
* @author ranjeeth.g
*/
public class AdmissionEnquiry extends LookupDispatchAction {
/* forward name="success" path="" */
private final static String SUCCESS = "success";
/**
* Provides the mapping from resource key to method name.
*
* @return Resource key / method name map.
*/
protected Map getKeyMethodMap() {
Map map = new HashMap();
map.put("button.admissionEnqiryList", "admissionEnqiryList");
map.put("button.image", "image");
map.put("button.delete", "delete");
return map;
}
/**
* Action called on Add button click
*/
public void admissionEnqiryList(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) {
// TODO: implement add method
try {
String stdutendserch = request.getParameter("admissionenquirysearch");
System.out.println("stdutendserch = " + stdutendserch);
Admissionservices as = new Admissionservices();
List<Enquirylistbean> stdserc = as.getStudentEnquirySerch(stdutendserch);
if (stdserc != null) {
response.setContentType("application/json");
String json = new Gson().toJson(stdserc);
System.out.println("json = " + json);
response.getWriter().print(json);
} else {
response.setContentType("application/json");
String json = new Gson().toJson(null);
response.getWriter().print(json);
}
} catch (Exception e) {
e.printStackTrace();
}
// return mapping.findForward(SUCCESS);
// return null;
}
/**
* Action called on Edit button click
*/
public void image(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) {
try {
System.out.println("Inside the image responce action");
response.setContentType("image/jpeg");
Academicyearmaster academicyearmaster = (Academicyearmaster) request.getSession().getAttribute("academicyear");
// String ss = getServlet().getServletContext().getRealPath("\\");
// String filePath = ss + "img\\paichart.png";
ServletOutputStream out = response.getOutputStream();
// System.out.println("out = " + out);
// String filePath2 = ss + "img\\paichart1.png";
// ExecutorService executor = Executors.newFixedThreadPool(2);
com.treamis.hr.employee.Sendded sendded = new com.treamis.hr.employee.Sendded(out, academicyearmaster);
sendded.image();
// executor.execute(sendded);
} catch (Exception e) {
e.printStackTrace();
}
// TODO: implement edit method
// return mapping.findForward(SUCCESS);
}
/**
* Action called on Delete button click
*/
public ActionForward delete(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) throws java.lang.Exception {
// TODO:implement delete method
return mapping.findForward(SUCCESS);
}
/* And your JSP would have the following format for submit buttons:
<html:form action="/test">
<html:submit property="method">
<bean:message key="button.add"/>
</html:submit>
<html:submit property="method">
<bean:message key="button.edit"/>
</html:submit>
<html:submit property="method">
<bean:message key="button.delete"/>
</html:submit>
</html:form>
*/
}
Java代碼生成圖像:
try{
ChartUtilities.writeChartAsJPEG(out, chart, 600, 400, info);
// System.out.println("file2 = " + file1);
} catch (Exception e) {
e.printStackTrace();
return "success";
} finally {
out.close();
}
答案在於Life cycle of Servlet
的Life cycle of Servlet
。 即使一個Servlet收到多個請求,也只會創建Servlet類的一個實例。
檢查是否有全局資源並進行修復。
或發布完整的servlet類以獲得更好的響應。
希望能幫助到你!
我認為,如果對每個保存在磁盤中的文件使用不同的文件名,則不會再出現此問題。
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