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Send array of objects from servlet to JSP

I want to send an array of my own objects to the JSP page upon request.

In this part of the code in the servlet, I will get my data, put it in an array of objects and set them for the request.

if (request.getParameter("todo").equals("show_article_list")) { try { Article[] articles = this.getArticleList(); request.setAttribute("articles", articles); RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("article/article_list.jsp"); dispatcher.forward(request, response); } catch (Exception e) { } } public Article[] getArticleList() throws Exception { db data = new db(); Connection con = data.OpenConnection(); PreparedStatement statement = con.prepareStatement("SELECT * FROM `article`"); ResultSet result = statement.executeQuery(); int size = 0; if (result != null) { if (result.last()) { size = result.getRow(); result.beforeFirst(); } } Article[] articles = new Article[size]; int i = 0; while(result.next()){ articles[i] = new Article ( result.getInt(1), result.getString(2), result.getString(3), result.getString(4)); i++; } return articles; }

This is my class:

 public class Article { public Integer getId(){return id;} public String getTitle(){return title;} public void setTitle(String title){this.title = title;} public String getText(){return text;} public void set(String text){this.text = text;} public String getDescription(){return description;} public void setDescription(String description){this.description= description;} private Integer id; private String title; private String text; private String description; public Article(Integer Id, String Title, String Text, String Description) { id = Id; title = Title; text = Text; description = Description; } }

On my JSP page, I want to create such an array of objects using request.getAttribute("articles"); How can i do this?

Should I use <jsp:useBean/> or something else? I tried to do this:

Article[] articles = request.getAttribute("articles");

But I have a mistake: Article cannot be resolved to a type

What have I done wrong?

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3 answers

You probably

  • forgot to import the Article class into JSP using <%@ page import="com.foo.bar.Article" %>
  • I forgot to pass the result of getAttribute () to the array of articles:

Article[] articles = (Article[]) request.getAttribute("articles");

Please note that you should not have Java code in the JSP. You must use JSP EL, JSTL and other custom tags. Read How to Avoid Java Code in JSP Files? .

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You should avoid using scripts using JSTL. Please go to the following example:

Example POJO class:

 public class Article { private int id; private String title; public Article(int id, String title) { this.id = id; this.title = title; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getTitle() { return title; } public void setTitle(String title) { this.title = title; } }

Servlet example:

 public class TestServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { Article[] articles = new Article[] {new Article(1, "Article one"), new Article(2, "Article two")}; request.setAttribute("articles", articles); RequestDispatcher dispatcher = request.getRequestDispatcher("/index.jsp"); dispatcher.forward(request, response); } }

Example JSP page:

 <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <c:forEach items="${articles}" var="article"> <c:out value="${article.id} ${article.title}"/><br /> </c:forEach> </body> </html>

HTML Result:

 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> 1 Article one<br /> 2 Article two<br /> </body> </html>

I hope this example can help you.

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 request.getAttribute("articles");

The above will always return a String, so you need to throw, use this

 Article[] articles = (Article[]) request.getAttribute("articles");

and import your Article class on jsp page, add this at import level

 <%@ page import="yourpackage.Article"%>
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Source: https://habr.com/ru/post/1397414/

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