bindtag.java

spring的源代码

/*
 * Copyright 2002-2005 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;

import java.beans.PropertyEditor;

import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.PageContext;

import org.springframework.validation.Errors;
import org.springframework.web.servlet.support.BindStatus;
import org.springframework.web.util.ExpressionEvaluationUtils;

/**
 * <p>Bind tag, supporting evaluation of binding errors for a certain
 * bean or bean property. Exports a "status" variable of type BindStatus,
 * both to Java expressions and JSP EL expressions.
 *
 * <p>Can be used to bind to any bean or bean property in the model.
 * The specified path determines whether the tag exposes the status of the
 * bean itself (showing object-level errors), a specific bean property
 * (showing field errors), or a matching set of bean properties (showing
 * all corresponding field errors).
 *
 * <p>The Errors object that has been bound using this tag is exposed,
 * as well as the bean property that this errors object applies to.
 * Nested tags like the transform tag can access those exposed properties.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #setPath
 * @see #getErrors
 * @see #getProperty
 * @see TransformTag
 */
public class BindTag extends HtmlEscapingAwareTag {

	/**
	 * Name of the exposed variable within the scope of this tag: "status".
	 */
	public static final String STATUS_VARIABLE_NAME = "status";


	private String path;

	private boolean ignoreNestedPath = false;

	private BindStatus status;

	private Object previousStatus;


	/**
	 * Set the path that this tag should apply. Can be a bean (e.g. "person")
	 * to get global errors, or a bean property (e.g. "person.name") to get
	 * field errors (also supporting nested fields and "person.na*" mappings).
	 * "person.*" will return all errors for the specified bean, both global
	 * and field errors.
	 * @see org.springframework.validation.Errors#getGlobalErrors
	 * @see org.springframework.validation.Errors#getFieldErrors
	 */
	public void setPath(String path) {
		this.path = path;
	}

	/**
	 * Return the path that this tag applies to.
	 */
	public String getPath() {
		return path;
	}

	/**
	 * Set whether to ignore a nested path, if any.
	 * Default is to not ignore.
	 */
	public void setIgnoreNestedPath(boolean ignoreNestedPath) {
	  this.ignoreNestedPath = ignoreNestedPath;
	}

	/**
	 * Return whether to ignore a nested path, if any.
	 */
	public boolean isIgnoreNestedPath() {
	  return ignoreNestedPath;
	}


	protected final int doStartTagInternal() throws Exception {
		String resolvedPath = ExpressionEvaluationUtils.evaluateString("path", getPath(), pageContext);

		if (!isIgnoreNestedPath()) {
			String nestedPath = (String) pageContext.getAttribute(
					NestedPathTag.NESTED_PATH_VARIABLE_NAME, PageContext.REQUEST_SCOPE);
			if (nestedPath != null) {
				resolvedPath = nestedPath + resolvedPath;
			}
		}

		try {
			this.status = new BindStatus(getRequestContext(), resolvedPath, isHtmlEscape());
		}
		catch (IllegalStateException ex) {
			throw new JspTagException(ex.getMessage());
		}

		// Save previous status value, for re-exposure at the end of this tag.
		this.previousStatus = pageContext.getAttribute(STATUS_VARIABLE_NAME);

		// Expose this tag's status object as PageContext attribute,
		// making it available for JSP EL.
		pageContext.setAttribute(STATUS_VARIABLE_NAME, this.status);

		return EVAL_BODY_INCLUDE;
	}

	public int doEndTag() {
		if (this.previousStatus != null) {
			// Reset previous status value.
			pageContext.setAttribute(STATUS_VARIABLE_NAME, this.previousStatus);
		}
		else {
			// Remove exposed status value.
			pageContext.removeAttribute(STATUS_VARIABLE_NAME);
		}

		return EVAL_PAGE;
	}


	/**
	 * Retrieve the property that this tag is currently bound to,
	 * or <code>null</code> if bound to an object rather than a specific property.
	 * Intended for cooperating nesting tags.
	 * @return the property that this tag is currently bound to,
	 * or <code>null</code> if none
	 */
	public final String getProperty() {
		return this.status.getExpression();
	}

	/**
	 * Retrieve the Errors instance that this tag is currently bound to.
	 * Intended for cooperating nesting tags.
	 * @return the current Errors instance, or <code>null</code> if none
	 */
	public final Errors getErrors() {
		return this.status.getErrors();
	}

	/**
	 * Retrieve the PropertyEditor for the property that this tag is
	 * currently bound to. Intended for cooperating nesting tags.
	 * @return the current PropertyEditor, or <code>null</code> if none
	 */
	public final PropertyEditor getEditor() {
		return this.status.getEditor();
	}


	public void doFinally() {
		super.doFinally();
		this.status = null;
		this.previousStatus = null;
	}

}