Member Avatar for thabotharshan

i am a student i am doing a jsp project for my J2EE module.I choose a auction web site 4 my project. I have a doubt Can I use the java beans into a Servlet.I uses the Beans into my Jsp Page by using USEBEAN but how can i use the sanme bean into a Servlet.????.
Please Reaply me.
Thanks
thabo

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  • Latest Post Latest Post by peter_budo

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Short answer: yes — a JavaBean is just a plain Java object, so servlets can create one, call its methods (including validation), and put it into request/session scope for a JSP to read. This builds on 's basic bean explanation and on 's point: learn the Java basics first so you understand objects, packages and classpaths.

A simple, practical pattern for form processing:

  • Servlet (controller) receives POST, sets request encoding, reads parameters.
  • Populate a bean (POJO) with setters or a constructor, then call a validate() method on the bean (or call a separate validator).
  • If validation fails, attach the bean and an errors map to the request and forward back to the form JSP.
  • If validation passes, persist the data and redirect to a success page (use redirect to avoid form resubmission).

Example bean and servlet sketches (not the same code already posted):

public class Bid implements java.io.Serializable {
    private String bidder;
    private double amount;
    public Bid() {}
    // getters/setters omitted for brevity

    public Map<String,String> validate() {
        Map<String,String> errors = new HashMap<>();
        if (bidder == null || bidder.trim().isEmpty()) errors.put("bidder","Required");
        if (amount <= 0) errors.put("amount","Must be > 0");
        return errors;
    }
}
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    req.setCharacterEncoding("UTF-8");
    Bid b = new Bid();
    b.setBidder(req.getParameter("bidder"));
    try { b.setAmount(Double.parseDouble(req.getParameter("amount"))); } catch(...) {}
    Map<String,String> errors = b.validate();
    if (!errors.isEmpty()) {
        req.setAttribute("errors", errors);
        req.setAttribute("bid", b);
        req.getRequestDispatcher("/bidForm.jsp").forward(req, resp);
        return;
    }
    // save and redirect
    resp.sendRedirect(req.getContextPath()+"/bidSuccess.jsp");
}

Tips and common pitfalls: make sure bean classes are in WEB-INF/classes (or a jar in WEB-INF/lib) and packages are correct; prefer servlets for control logic and JSP+JSTL/EL for view (avoid scriptlets); always set request encoding for POST forms; and avoid storing transient request state only in session. For more depth, study the servlet/JSP MVC pattern and practice small examples before wiring a full auction site. ’s advice to read a good book/tutorial first is sound.

Recommended Answers

All 5 Replies

Member Avatar for jwenting

Read and understand the java tutorial first of all.
You seem to have no grasp of what a javabean is, which means you don't understand the basics of the language.

Member Avatar for thabotharshan

Read and understand the java tutorial first of all.
You seem to have no grasp of what a javabean is, which means you don't understand the basics of the language.

i didnt yet understand what is bean...i also show some tutorials....can you give a small explanation about bean and how it is differ from servlet?and give and example for a form processing

Member Avatar for sapna suresh

JavaBeans are Java classes which adhere to an extremely simple coding convention. All you have to do is to implement java.io.Serializable interface, use a public empty argument constructor and provide public getter and setter methods to get and set the values of private variables ( properties )

Sample Example Code:

public class SimpleBean implements java.io.Serializable {

	/* Properties */
	private String name = null;
	private int age = 0;

	/* Empty Constructor */
	public SimpleBean() {}

	/* Getter and Setter Methods */
	public String getName() {
		return name;
	}

	public void setName(String s) {
		name = s;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int i) {
		age = i;
	}
}
Edited by Ezzaral because: Added code tags. Please use them to format any code that you post.
Member Avatar for thabotharshan

Thank u Sapna Suresh.. But i have a doubt can we invoke some other user defined method into the beans?.Because you said the bean is a java class.... i want to make validation to my inputs..it means ,for an example i passes all the input value to a bean from the form i have made.i want to validate my inputs..can you explain this senario??please give a example cording for your explain...

Member Avatar for peter_budo

Thank u Sapna Suresh.. But i have a doubt can we invoke some other user defined method into the beans?.Because you said the bean is a java class.... i want to make validation to my inputs..it means ,for an example i passes all the input value to a bean from the form i have made.i want to validate my inputs..can you explain this senario??please give a example cording for your explain...

Then you should seriously pick up some book and start learning as jwenting already recommended as you obviously do not have essential background

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