Assume that when a user accesses to my website, then he will see a lot of images which have stored in the database before. I know how to do that in JSP Scriptlet, and I also know how to fetch and retrieve data from the database in JSTL when the user submit a form by using servlet. But I don't know how to do it in JSTL without user submitting a form.
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share code, what have you did already.Braj– Braj2014-07-31 05:12:37 +00:00Commented Jul 31, 2014 at 5:12
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1I dont have the JSTL code. I only have have jsp scriptlet code, which I retrieve and store data into an hashmap, then inside the jsp body, I get and display the data from hashmap so that the user will be able to see that data. Since there are a lot of articles recommend using JSTL and JSF instead of JSP scriptlet, I want to learn and convert my code to JSTL. But seem like JSTL lacking of flexibility when involving custom java class.user3819470– user38194702014-07-31 05:25:29 +00:00Commented Jul 31, 2014 at 5:25
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2 Answers
Yes, You can use JSTL & EL. For database access use JSTL SQL Tag library.
How to display images in JSP that is stored in database?
I hope you are using BLOB type column to store images in database. Simply hit a Servlet passing id of the records and send byte[] in response.
I have created separate request for each image for better user experience as well.
Note: It's better to move the database code in the Servlet.
JSP:
<%@ taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<sql:setDataSource var="webappDataSource"
driver="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost:3306/test"
user="root" password="root" />
<sql:query dataSource="${webappDataSource}"
sql="select id,username from users" var="result" />
<table width="100%" border="1">
<c:forEach var="row" items="${result.rows}">
<tr>
<td>${row.id}</td>
<td>${row.username}</td>
<td>
<img src="${pageContext.servletContext.contextPath }/photoServlet?id=${row.id}" />
</td>
</tr>
</c:forEach>
</table>
Servlet (PhotoServlet.java):
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
final String DB_URL = "jdbc:mysql://localhost:3306/test";
final String User = "root";
final String Password = "root";
try {
Class.forName(JDBC_DRIVER);
Connection conn = DriverManager.getConnection(DB_URL, User, Password);
PreparedStatement stmt = conn.prepareStatement("select photo from users where id=?");
stmt.setLong(1, Long.valueOf(request.getParameter("id")));
ResultSet rs = stmt.executeQuery();
if (rs.next()) {
response.getOutputStream().write(rs.getBytes("photo"));
}
conn.close();
} catch (Exception e) {
e.printStackTrace();
}
}
web.xml:
<servlet>
<servlet-name>PhotoServlet</servlet-name>
<servlet-class>com.server.servlet.PhotoServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>PhotoServlet</servlet-name>
<url-pattern>/photoServlet</url-pattern>
</servlet-mapping>
Table structure: (users)
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| username | varchar(30) | YES | | NULL | |
| password | varchar(20) | YES | | NULL | |
| photo | blob | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
5 Comments
user3819470
Thank you, I am cleared now.
Braj
If the issue is resolved then close the thread. As per your question list, you haven't accepted any answer.
user3819470
Oh, sorry. I didnt know there is that option.
Abhishek Shandilya
what can i do if i have to get multiple images for same id
rhitz
(+1) - One question : You were needed to query the database twice, isn't their a way to do this in a single query ?
If your question is about displaying database content on JSP page using JSTL tags and if you are using native style JDBC database connection (not jpa or hibernate), take a look:
// make a class for you database table mapping
// assume you have id,name,salary in employee database table , make a Java class for it
class Employee{
int id;
String name;
float salary;
// now getter setter for fields
public int getId(){
return this.id;
}
public void setId(int id){
this.id = id;
}
public String getName(){
return this.name;
}
public void setName(String name){
this.name = name;
}
public float getSalary(){
return this.salary;
}
public void setSalary(int salary){
this.salary = salary;
}
}
// now in your servlet class make a list of Employee class and set data from data base
List<Employee> empList = new ArrayList<Employee>();
// asume your db connection and query is here
ResultSet rs = your_result_Set
while(rs.next()){
Employee emp = new Employee();
emp.setId(rs.getInt("id"));
emp.setName(rs.getString("name"));
em.setSalary(rs.getFloat("slary"));
empList.add(em);
}
request.setAttribute("empList",empList);
request.getRequestDispacher("your_jsp_path").forward(request,response);
// now in your jsp add <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> on top of jsp
<table>
<c:forEach items="${empList}" var="e" >
<tr>
<td>${e.id}</td>
<td>${e.name}</td>
<td>${e.salary}</td>
</tr>
</c:forEach>
</table>
Custom MVC using servlet and jsp. Take a look using servlet 3.0 or higher
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(name="login", urlPatterns={"/login"})
public class NewServlet extends HttpServlet {
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try{
// do your login logic here
request.setAttribute("message","login failed");
request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);
}
catch(Exception exp){
}
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}
// now in login.jsp placed in WEB-INF/jsp
<span>${message}</span><!-- message is request attribute here assigned in servlet-->
Now whenever you call login url request 1st comes to login servlet after that transferred to jsp
4 Comments
user3819470
How can the data be stored into the empList? Will the servlet class run, retrieve and store data into the empList automatically when the page is opened and without user request? I got a bit confused here.
Vicky
Use your servlet as Controller. for each URL in your project You have to create two file one is Servlet and 2nd is JSP. Now put your JSP in WEB-INF/jsp/ (create jsp in this folder). Now your servlet has a url that can publicly accessible assume "/login/"
Vicky
On Login Servlet you have to do all logic and put data in request attribute and do foward to jsp page Eg. on servlet file do request.getRequestDispacher("WEB-INF/views/login.jsp").forward(request.response); See new update in answer
user3819470
I see. Thank you for your instruction
