ThrowawayFormController: the throwaway with a form

[adamjk]

I wanted a throwaway controller that I could use with something that had binding, validation and form and successviews, for purposes of a searching dialog. I didn't want to create a needless command object class for a search form. So here's the product... don't yell at me if it was obvious all along or inherently flawed

package com.xx.xxx.web.controller;

import javax.servlet.http.HttpServletRequest;

import org.springframework.web.servlet.mvc.SimpleFormController;

/**
 * <p>
 * Controller that extends <code>SimpleFormController</code> where command
 * object is instance of itself. Class properties of controller can be binded to
 * form fields and validated.
 * </p>
 * 
 * <p>
 * Form should be configured as a non-singleton bean. There is no need to set
 * configuration property commandClass property as command always refers to the
 * controller's class. In fact, setting it to the wrong class will cause an a
 * thrown <code>ServletException</code> when
 * &#123;@link #checkCommand checkCommand&#40;&#41;&#125; is called to match the command object's
 * class and the configured commandClass property. Configuration property
 * commandName can still be set to refer to command object.
 * </p>
 */
public abstract class ThrowawayFormController extends SimpleFormController &#123;

    /**
     * Finalized method to only return this instance of controller.
     */
    protected final Object formBackingObject&#40;HttpServletRequest request&#41;
            throws Exception &#123;
        return this;
    &#125;
&#125;

Here's an example bean configuration and class that extends the abstract class.

package com.xx.xxx.web.controller;

import java.util.ArrayList;
import java.util.List;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.hibernate.criterion.Expression;
import org.hibernate.criterion.MatchMode;
import org.springframework.util.StringUtils;
import org.springframework.validation.BindException;
import org.springframework.web.servlet.ModelAndView;

import com.xx.xxx.persistence.SubjectDao;

/**
 * Controller accepts criteria parameters that are used to search for subjects
 * and return list in a search results view.
 */
public class SearchSubjectController extends ThrowawayFormController {

    private SubjectDao subjectDao;

    /**
     * Bind variable for subject's givenName search criteria
     */
    private String givenName;
    
    /**
     * Bind variable for subject's surname search criteria
     */
    private String surname;

    /**
     * Takes criteria and creates a collection of criterion to pass to 
     * dao/manager to find subjects.
     * 
     */
    protected ModelAndView onSubmit(HttpServletRequest request,
            HttpServletResponse response, Object command, BindException errors)
            throws Exception {
        ArrayList criteria = new ArrayList();
        List subjects = null;
        if (StringUtils.hasText(this.givenName)) {
            criteria.add(Expression.like("givenName", this.givenName,
                    MatchMode.ANYWHERE).ignoreCase());
        }
        if (StringUtils.hasText(this.surname)) {
            criteria.add(Expression.like("surname", this.surname,
                    MatchMode.ANYWHERE).ignoreCase());
        }

        subjects = subjectDao.findSubjectsByCriteria(criteria);
        return new ModelAndView(getSuccessView(), "subjects", subjects);
    }

    public void setSubjectDao(SubjectDao subjectDao) {
        this.subjectDao = subjectDao;
    }

    public String getGivenName() {
        return givenName;
    }

    public void setGivenName(String givenName) {
        this.givenName = givenName;
    }

    public String getSurname() {
        return surname;
    }

    public void setSurname(String surname) {
        this.surname = surname;
    }

}

       <bean name="/searchSubjects.htm"
		class="com.xx.xxx.web.controller.SearchSubjectController"
		singleton="false">
		<property name="commandName">
			<value>subjectSearch</value>
		</property>
		<property name="subjectDao">
			<ref bean="subjectManager" />
		</property>
		<property name="formView">
			<value>subjectSearchForm</value>
		</property>
		<property name="successView">
			<value>subjectSearchResults</value>
		</property>
		<property name="validator">
			<ref bean="beanValidator" />
		</property>
	</bean>

[Colin Yates]

interesting

I'm not sure I get the benefit of what you have done though If you don't want the overhead of creating/using a strongly typed form, then why not simply use a Map as your command object?
AFAIK spring will happily bind to [code]<spring:bind name="command[key]"/>[code]

Also, I don't think you have *changed* what is happening, rather you have moved where it is happening. You still have a strongly typed form, but it is held on the controller, not in a seperate class

I haven't had my coffee this morning so I might be being mean

[adamjk]

Yatesco,

Yer right about moving things around. My intention was to avoid creation of extra classes, and avoid clutter. The idea of a map would definitely meet the same need. One of the other reasons for using the controller as the command object was to validate with commons validator. I haven't looked into validating map objects in commons validator, but if it was possible the concept of using a map would meet all my requirements for writing the ThrowawayFormController.

Adam