Spring Framework example source code file (FormTag.java)

This example Spring Framework source code file (FormTag.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

accept_charset_attribute, default_method, enctype_attribute, http, illegalargumentexception, jspexception, jspexception, model_attribute, request, response, servlet, string, string, target_attribute, target_attribute, the, unsupportedoperationexception, uri

The Spring Framework FormTag.java source code

/*
 * Copyright 2002-2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.tags.form;

import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;

import org.springframework.beans.PropertyAccessor;
import org.springframework.core.Conventions;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.util.HtmlUtils;

/**
 * Databinding-aware JSP tag for rendering an HTML '<code>form' whose
 * inner elements are bound to properties on a <em>form object.
 *
 * <p>Users should place the form object into the
 * {@link org.springframework.web.servlet.ModelAndView ModelAndView} when
 * populating the data for their view. The name of this form object can be
 * configured using the {@link #setModelAttribute "modelAttribute"} property.
 *
 * <p>The default value for the {@link #setModelAttribute "modelAttribute"}
 * property is '<code>command' which corresponds to the default name
 * when using the
 * {@link org.springframework.web.servlet.mvc.SimpleFormController SimpleFormController}.
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @since 2.0
 * @see org.springframework.web.servlet.mvc.SimpleFormController
 */
public class FormTag extends AbstractHtmlElementTag {

	/** The default HTTP method using which form values are sent to the server: "post" */
	private static final String DEFAULT_METHOD = "post";

	/** The default attribute name: "command" */
	public static final String DEFAULT_COMMAND_NAME = "command";

	private static final String ONSUBMIT_ATTRIBUTE = "onsubmit";

	private static final String ONRESET_ATTRIBUTE = "onreset";

	private static final String ACTION_ATTRIBUTE = "action";

	private static final String METHOD_ATTRIBUTE = "method";

	private static final String TARGET_ATTRIBUTE = "target";

	private static final String ENCTYPE_ATTRIBUTE = "enctype";

	private static final String ACCEPT_CHARSET_ATTRIBUTE = "accept-charset";

	/** The name of the '<code>modelAttribute' setting */
	private static final String MODEL_ATTRIBUTE = "modelAttribute";

	/**
	 * The name of the {@link javax.servlet.jsp.PageContext} attribute under which the
	 * form object name is exposed.
	 */
	public static final String MODEL_ATTRIBUTE_VARIABLE_NAME =
			Conventions.getQualifiedAttributeName(AbstractFormTag.class, MODEL_ATTRIBUTE);


	private TagWriter tagWriter;

	private String modelAttribute = DEFAULT_COMMAND_NAME;

	private String name;

	private String action;

	private String method = DEFAULT_METHOD;

	private String target;

	private String enctype;

	private String onsubmit;

	private String onreset;

	private String acceptCharset;

	/** Caching a previous nested path, so that it may be reset */
	private String previousNestedPath;


	/**
	 * Set the name of the form attribute in the model.
	 * <p>May be a runtime expression.
	 */
	public void setModelAttribute(String modelAttribute) {
		this.modelAttribute = modelAttribute;
	}

	/**
	 * Get the name of the form attribute in the model.
	 */
	protected String getModelAttribute() {
		return this.modelAttribute;
	}

	/**
	 * Set the name of the form attribute in the model.
	 * <p>May be a runtime expression.
	 * @see #setModelAttribute
	 */
	public void setCommandName(String commandName) {
		this.modelAttribute = commandName;
	}

	/**
	 * Get the name of the form attribute in the model.
	 * @see #getModelAttribute
	 */
	protected String getCommandName() {
		return this.modelAttribute;
	}

	/**
	 * Set the value of the '<code>name' attribute.
	 * <p>May be a runtime expression.
	 * <p>Name is not a valid attribute for form on XHTML 1.0. However,
	 * it is sometimes needed for backward compatibility.
	 */
	public void setName(String name) {
		this.name = name;
	}

	/**
	 * Get the value of the '<code>name' attribute.
	 */
	protected String getName() throws JspException {
		return this.name;
	}

	/**
	 * Set the value of the '<code>action' attribute.
	 * <p>May be a runtime expression.
	 */
	public void setAction(String action) {
		this.action = (action != null ? action : "");
	}

	/**
	 * Get the value of the '<code>action' attribute.
	 */
	protected String getAction() {
		return this.action;
	}

	/**
	 * Set the value of the '<code>method' attribute.
	 * <p>May be a runtime expression.
	 */
	public void setMethod(String method) {
		this.method = method;
	}

	/**
	 * Get the value of the '<code>method' attribute.
	 */
	protected String getMethod() {
		return this.method;
	}

	/**
	 * Set the value of the '<code>target' attribute.
	 * <p>May be a runtime expression.
	 */
	public void setTarget(String target) {
		this.target = target;
	}

	/**
	 * Get the value of the '<code>target' attribute.
	 */
	public String getTarget() {
		return this.target;
	}

	/**
	 * Set the value of the '<code>enctype' attribute.
	 * <p>May be a runtime expression.
	 */
	public void setEnctype(String enctype) {
		this.enctype = enctype;
	}

	/**
	 * Get the value of the '<code>enctype' attribute.
	 */
	protected String getEnctype() {
		return this.enctype;
	}

	/**
	 * Set the value of the '<code>acceptCharset' attribute.
	 * <p>May be a runtime expression.
	 */
	public void setAcceptCharset(String acceptCharset) {
		this.acceptCharset = acceptCharset;
	}

	/**
	 * Get the value of the '<code>acceptCharset' attribute.
	 */
	protected String getAcceptCharset() {
		return this.acceptCharset;
	}

	/**
	 * Set the value of the '<code>onsubmit' attribute.
	 * <p>May be a runtime expression.
	 */
	public void setOnsubmit(String onsubmit) {
		this.onsubmit = onsubmit;
	}

	/**
	 * Get the value of the '<code>onsubmit' attribute.
	 */
	protected String getOnsubmit() {
		return this.onsubmit;
	}

	/**
	 * Set the value of the '<code>onreset' attribute.
	 * <p>May be a runtime expression.
	 */
	public void setOnreset(String onreset) {
		this.onreset = onreset;
	}

	/**
	 * Get the value of the '<code>onreset' attribute.
	 */
	protected String getOnreset() {
		return this.onreset;
	}


	/**
	 * Writes the opening part of the block	'<code>form' tag and exposes
	 * the form object name in the {@link javax.servlet.jsp.PageContext}.
	 * @param tagWriter the {@link TagWriter} to which the form content is to be written
	 * @return {@link javax.servlet.jsp.tagext.Tag#EVAL_BODY_INCLUDE}
	 */
	protected int writeTagContent(TagWriter tagWriter) throws JspException {
		this.tagWriter = tagWriter;

		tagWriter.startTag("form");
		writeDefaultAttributes(tagWriter);
		tagWriter.writeAttribute(ACTION_ATTRIBUTE, resolveAction());
		writeOptionalAttribute(tagWriter, METHOD_ATTRIBUTE, getMethod());
		writeOptionalAttribute(tagWriter, TARGET_ATTRIBUTE, getTarget());
		writeOptionalAttribute(tagWriter, ENCTYPE_ATTRIBUTE, getEnctype());
		writeOptionalAttribute(tagWriter, ONSUBMIT_ATTRIBUTE, getOnsubmit());
		writeOptionalAttribute(tagWriter, ONRESET_ATTRIBUTE, getOnreset());
		writeOptionalAttribute(tagWriter, ACCEPT_CHARSET_ATTRIBUTE, getAcceptCharset());

		tagWriter.forceBlock();

		// Expose the form object name for nested tags...
		String modelAttribute = resolveModelAttribute();
		this.pageContext.setAttribute(MODEL_ATTRIBUTE_VARIABLE_NAME, modelAttribute, PageContext.REQUEST_SCOPE);
		this.pageContext.setAttribute(COMMAND_NAME_VARIABLE_NAME, modelAttribute, PageContext.REQUEST_SCOPE);

		// Save previous nestedPath value, build and expose current nestedPath value.
		// Use request scope to expose nestedPath to included pages too.
		this.previousNestedPath =
				(String) this.pageContext.getAttribute(NESTED_PATH_VARIABLE_NAME, PageContext.REQUEST_SCOPE);
		this.pageContext.setAttribute(NESTED_PATH_VARIABLE_NAME,
				modelAttribute + PropertyAccessor.NESTED_PROPERTY_SEPARATOR, PageContext.REQUEST_SCOPE);

		return EVAL_BODY_INCLUDE;
	}

	/**
	 * Autogenerated IDs correspond to the form object name.
	 */
	protected String autogenerateId() throws JspException {
		return resolveModelAttribute();
	}

	/**
	 * {@link #evaluate Resolves} and returns the name of the form object.
	 * @throws IllegalArgumentException if the form object resolves to <code>null
	 */
	protected String resolveModelAttribute() throws JspException {
		Object resolvedModelAttribute = evaluate(MODEL_ATTRIBUTE, getModelAttribute());
		if (resolvedModelAttribute == null) {
			throw new IllegalArgumentException(MODEL_ATTRIBUTE + " must not be null");
		}
		return (String) resolvedModelAttribute;
	}

	/**
	 * Resolve the value of the '<code>action' attribute.
	 * <p>If the user configured an 'action' value then
	 * the result of evaluating this value is used. Otherwise, the
	 * {@link org.springframework.web.servlet.support.RequestContext#getRequestUri() originating URI}
	 * is used.
	 * @return the value that is to be used for the '<code>action' attribute
	 */
	protected String resolveAction() throws JspException {
		String action = getAction();
		if (StringUtils.hasText(action)) {
			return getDisplayString(evaluate(ACTION_ATTRIBUTE, action));
		}
		else {
			String requestUri = getRequestContext().getRequestUri();
			ServletResponse response = this.pageContext.getResponse();
			if (response instanceof HttpServletResponse) {
				requestUri = ((HttpServletResponse) response).encodeURL(requestUri);
				String queryString = getRequestContext().getQueryString();
				if (StringUtils.hasText(queryString)) {
					requestUri += "?" + HtmlUtils.htmlEscape(queryString);
				}
			}
			if (StringUtils.hasText(requestUri)) {
				return requestUri;
			}
			else {
				throw new IllegalArgumentException("Attribute 'action' is required. " +
						"Attempted to resolve against current request URI but request URI was null.");
			}
		}
	}


	/**
	 * Closes the '<code>form' block tag and removes the form object name
	 * from the {@link javax.servlet.jsp.PageContext}.
	 */
	public int doEndTag() throws JspException {
		this.tagWriter.endTag();
		this.pageContext.removeAttribute(MODEL_ATTRIBUTE_VARIABLE_NAME, PageContext.REQUEST_SCOPE);
		this.pageContext.removeAttribute(COMMAND_NAME_VARIABLE_NAME, PageContext.REQUEST_SCOPE);
		if (this.previousNestedPath != null) {
			// Expose previous nestedPath value.
			this.pageContext.setAttribute(NESTED_PATH_VARIABLE_NAME, this.previousNestedPath, PageContext.REQUEST_SCOPE);
		}
		else {
			// Remove exposed nestedPath value.
			this.pageContext.removeAttribute(NESTED_PATH_VARIABLE_NAME, PageContext.REQUEST_SCOPE);
		}
		return EVAL_PAGE;
	}

	/**
	 * Clears the stored {@link TagWriter}.
	 */
	public void doFinally() {
		super.doFinally();
		this.tagWriter = null;
		this.previousNestedPath = null;
	}


	/**
	 * Override resolve CSS class since error class is not supported.
	 */
	protected String resolveCssClass() throws JspException {
		return ObjectUtils.getDisplayString(evaluate("cssClass", getCssClass()));
	}

	/**
	 * Unsupported for forms.
	 * @throws UnsupportedOperationException always
	 */
	public void setPath(String path) {
		throw new UnsupportedOperationException("The 'path' attribute is not supported for forms");
	}

	/**
	 * Unsupported for forms.
	 * @throws UnsupportedOperationException always
	 */
	public void setCssErrorClass(String cssErrorClass) {
		throw new UnsupportedOperationException("The 'cssErrorClass' attribute is not supported for forms");
	}

}