Spring Framework example source code file (ErrorsTag.java)

This example Spring Framework source code file (ErrorsTag.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

abstracthtmlelementbodytag, arraylist, errorstag, http, illegalstateexception, jsp, jspexception, jspexception, list, messages_attribute, object, object, servlet, span_tag, span_tag, string, string, util

The Spring Framework ErrorsTag.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 java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.BodyTag;

import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;

/**
 * Form tag for displaying errors for a particular field or object.
 *
 * <p>This tag supports three main usage patterns:
 *
 * <ol>
 *	<li>Field only - set 'path' to the field name (or path)
 *	<li>Object errors only - omit 'path'
 *	<li>All errors - set 'path' to '*'
 * </ol>
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @author Rick Evans
 * @since 2.0
 */
public class ErrorsTag extends AbstractHtmlElementBodyTag implements BodyTag {

	/**
	 * The key under which this tag exposes error messages in
	 * the {@link PageContext#PAGE_SCOPE page context scope}.
	 */
	public static final String MESSAGES_ATTRIBUTE = "messages";

	/**
	 * The HTML '<code>span' tag.
	 */
	public static final String SPAN_TAG = "span";


	private String element = SPAN_TAG;

	private String delimiter = "<br/>";

	/**
	 * Stores any value that existed in the 'errors messages' before the tag was started.
	 */
	private Object oldMessages;

	private boolean errorMessagesWereExposed;


	/**
	 * Set the HTML element must be used to render the error messages.
	 * <p>Defaults to an HTML '<span/>' tag.
	 */
	public void setElement(String element) {
		Assert.hasText(element, "'element' cannot be null or blank");
		this.element = element;
	}

	/**
	 * Get the HTML element must be used to render the error messages.
	 */
	public String getElement() {
		return this.element;
	}

	/**
	 * Set the delimiter to be used between error messages.
	 * <p>Defaults to an HTML '<br/>' tag.
	 */
	public void setDelimiter(String delimiter) {
		this.delimiter = delimiter;
	}

	/**
	 * Return the delimiter to be used between error messages.
	 */
	public String getDelimiter() {
		return this.delimiter;
	}


	/**
	 * Get the value for the HTML '<code>name' attribute.
	 * <p>Simply returns null because the 'name' attribute
	 * is not a validate attribute for the '<code>span' element.
	 */
	protected String getName() throws JspException {
		return null;
	}

	/**
	 * Get the value for the HTML '<code>id' attribute.
	 * <p>Appends '.errors' to the value returned by {@link #getPropertyPath()}
	 * or to the model attribute name if the <code><form:errors/> tag's
	 * '<code>path' attribute has been omitted.
	 * @return the value for the HTML '<code>id' attribute
	 * @see #getPropertyPath()
	 */
	protected String autogenerateId() throws JspException {
		String path = getPropertyPath();
		if ("".equals(path)) {
			path = (String) this.pageContext.getAttribute(
					FormTag.MODEL_ATTRIBUTE_VARIABLE_NAME, PageContext.REQUEST_SCOPE);
		}
		return path + ".errors";
	}

	/**
	 * Should rendering of this tag proceed at all?
	 * <p>Only renders output when there are errors for the configured {@link #setPath path}.
	 * @return <code>true only when there are errors for the configured {@link #setPath path}
	 */
	protected boolean shouldRender() throws JspException {
		try {
			return getBindStatus().isError();
		}
		catch (IllegalStateException ex) {
			// Neither BindingResult nor target object available.
			return false;
		}
	}

	protected void renderDefaultContent(TagWriter tagWriter) throws JspException {
		tagWriter.startTag(getElement());
		writeDefaultAttributes(tagWriter);
		String delimiter = ObjectUtils.getDisplayString(evaluate("delimiter", getDelimiter()));
		String[] errorMessages = getBindStatus().getErrorMessages();
		for (int i = 0; i < errorMessages.length; i++) {
			String errorMessage = errorMessages[i];
			if (i > 0) {
				tagWriter.appendValue(delimiter);
			}
			tagWriter.appendValue(getDisplayString(errorMessage));
		}
		tagWriter.endTag();
	}

	/**
	 * Exposes any bind status error messages under {@link #MESSAGES_ATTRIBUTE this key}
	 * in the {@link PageContext#PAGE_SCOPE}.
	 * <p>Only called if {@link #shouldRender()} returns true.
	 * @see #removeAttributes()
	 */
	protected void exposeAttributes() throws JspException {
		List errorMessages = new ArrayList();
		errorMessages.addAll(Arrays.asList(getBindStatus().getErrorMessages()));
		this.oldMessages = this.pageContext.getAttribute(MESSAGES_ATTRIBUTE, PageContext.PAGE_SCOPE);
		this.pageContext.setAttribute(MESSAGES_ATTRIBUTE, errorMessages, PageContext.PAGE_SCOPE);
		this.errorMessagesWereExposed = true;
	}

	/**
	 * Removes any bind status error messages that were previously stored under
	 * {@link #MESSAGES_ATTRIBUTE this key} in the {@link PageContext#PAGE_SCOPE}.
	 * @see #exposeAttributes()
	 */
	protected void removeAttributes() {
		if (this.errorMessagesWereExposed) {
			if (this.oldMessages != null) {
				this.pageContext.setAttribute(MESSAGES_ATTRIBUTE, this.oldMessages, PageContext.PAGE_SCOPE);
				this.oldMessages = null;
			}
			else {
				this.pageContext.removeAttribute(MESSAGES_ATTRIBUTE, PageContext.PAGE_SCOPE);
			}
		}
	}

}