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Spring Framework example source code file (AbstractView.java)

This example Spring Framework source code file (AbstractView.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

csv, exception, http, httpservletrequest, httpservletresponse, illegalargumentexception, illegalargumentexception, iterator, map, map, object, object, request, requestcontext, response, servlet, string, string, util

The Spring Framework AbstractView.java source code

/*
 * Copyright 2002-2007 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.view;

import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Properties;
import java.util.StringTokenizer;

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

import org.springframework.beans.factory.BeanNameAware;
import org.springframework.util.CollectionUtils;
import org.springframework.web.context.support.WebApplicationObjectSupport;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.support.RequestContext;

/**
 * Abstract base class for {@link org.springframework.web.servlet.View}
 * implementations. Subclasses should be JavaBeans, to allow for
 * convenient configuration as Spring-managed bean instances.
 *
 * <p>Provides support for static attributes, to be made available to the view,
 * with a variety of ways to specify them. Static attributes will be merged
 * with the given dynamic attributes (the model that the controller returned)
 * for each render operation.
 *
 * <p>Extends {@link WebApplicationObjectSupport}, which will be helpful to
 * some views. Subclasses just need to implement the actual rendering.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #setAttributes
 * @see #setAttributesMap
 * @see #renderMergedOutputModel
 */
public abstract class AbstractView extends WebApplicationObjectSupport implements View, BeanNameAware {

	/** Default content type. Overridable as bean property. */
	public static final String DEFAULT_CONTENT_TYPE = "text/html;charset=ISO-8859-1";


	private String beanName;

	private String contentType = DEFAULT_CONTENT_TYPE;

	private String requestContextAttribute;

	/** Map of static attributes, keyed by attribute name (String) */
	private final Map	staticAttributes = new HashMap();


	/**
	 * Set the view's name. Helpful for traceability.
	 * <p>Framework code must call this when constructing views.
	 */
	public void setBeanName(String beanName) {
		this.beanName = beanName;
	}

	/**
	 * Return the view's name. Should never be <code>null,
	 * if the view was correctly configured.
	 */
	public String getBeanName() {
		return this.beanName;
	}

	/**
	 * Set the content type for this view.
	 * Default is "text/html;charset=ISO-8859-1".
	 * <p>May be ignored by subclasses if the view itself is assumed
	 * to set the content type, e.g. in case of JSPs.
	 */
	public void setContentType(String contentType) {
		this.contentType = contentType;
	}

	/**
	 * Return the content type for this view.
	 */
	public String getContentType() {
		return this.contentType;
	}

	/**
	 * Set the name of the RequestContext attribute for this view.
	 * Default is none.
	 */
	public void setRequestContextAttribute(String requestContextAttribute) {
		this.requestContextAttribute = requestContextAttribute;
	}

	/**
	 * Return the name of the RequestContext attribute, if any.
	 */
	public String getRequestContextAttribute() {
		return this.requestContextAttribute;
	}

	/**
	 * Set static attributes as a CSV string.
	 * Format is: attname0={value1},attname1={value1}
	 * <p>"Static" attributes are fixed attributes that are specified in
	 * the View instance configuration. "Dynamic" attributes, on the other hand,
	 * are values passed in as part of the model.
	 */
	public void setAttributesCSV(String propString) throws IllegalArgumentException {
		if (propString != null) {
			StringTokenizer st = new StringTokenizer(propString, ",");
			while (st.hasMoreTokens()) {
				String tok = st.nextToken();
				int eqIdx = tok.indexOf("=");
				if (eqIdx == -1) {
					throw new IllegalArgumentException("Expected = in attributes CSV string '" + propString + "'");
				}
				if (eqIdx >= tok.length() - 2) {
					throw new IllegalArgumentException(
							"At least 2 characters ([]) required in attributes CSV string '" + propString + "'");
				}
				String name = tok.substring(0, eqIdx);
				String value = tok.substring(eqIdx + 1);

				// Delete first and last characters of value: { and }
				value = value.substring(1);
				value = value.substring(0, value.length() - 1);

				addStaticAttribute(name, value);
			}
		}
	}

	/**
	 * Set static attributes for this view from a
	 * <code>java.util.Properties object.
	 * <p>"Static" attributes are fixed attributes that are specified in
	 * the View instance configuration. "Dynamic" attributes, on the other hand,
	 * are values passed in as part of the model.
	 * <p>This is the most convenient way to set static attributes. Note that
	 * static attributes can be overridden by dynamic attributes, if a value
	 * with the same name is included in the model.
	 * <p>Can be populated with a String "value" (parsed via PropertiesEditor)
	 * or a "props" element in XML bean definitions.
	 * @see org.springframework.beans.propertyeditors.PropertiesEditor
	 */
	public void setAttributes(Properties attributes) {
		CollectionUtils.mergePropertiesIntoMap(attributes, this.staticAttributes);
	}

	/**
	 * Set static attributes for this view from a Map. This allows to set
	 * any kind of attribute values, for example bean references.
	 * <p>"Static" attributes are fixed attributes that are specified in
	 * the View instance configuration. "Dynamic" attributes, on the other hand,
	 * are values passed in as part of the model.
	 * <p>Can be populated with a "map" or "props" element in XML bean definitions.
	 * @param attributes Map with name Strings as keys and attribute objects as values
	 */
	public void setAttributesMap(Map attributes) {
		if (attributes != null) {
			Iterator it = attributes.entrySet().iterator();
			while (it.hasNext()) {
				Map.Entry entry = (Map.Entry) it.next();
				Object key = entry.getKey();
				if (!(key instanceof String)) {
					throw new IllegalArgumentException(
							"Invalid attribute key [" + key + "]: only Strings allowed");
				}
				addStaticAttribute((String) key, entry.getValue());
			}
		}
	}

	/**
	 * Allow Map access to the static attributes of this view,
	 * with the option to add or override specific entries.
	 * <p>Useful for specifying entries directly, for example via
	 * "attributesMap[myKey]". This is particularly useful for
	 * adding or overriding entries in child view definitions.
	 */
	public Map getAttributesMap() {
		return this.staticAttributes;
	}

	/**
	 * Add static data to this view, exposed in each view.
	 * <p>"Static" attributes are fixed attributes that are specified in
	 * the View instance configuration. "Dynamic" attributes, on the other hand,
	 * are values passed in as part of the model.
	 * <p>Must be invoked before any calls to render.
	 * @param name the name of the attribute to expose
	 * @param value the attribute value to expose
	 * @see #render
	 */
	public void addStaticAttribute(String name, Object value) {
		this.staticAttributes.put(name, value);
	}

	/**
	 * Return the static attributes for this view. Handy for testing.
	 * <p>Returns an unmodifiable Map, as this is not intended for
	 * manipulating the Map but rather just for checking the contents.
	 * @return the static attributes in this view
	 */
	public Map getStaticAttributes() {
		return Collections.unmodifiableMap(this.staticAttributes);
	}


	/**
	 * Prepares the view given the specified model, merging it with static
	 * attributes and a RequestContext attribute, if necessary.
	 * Delegates to renderMergedOutputModel for the actual rendering.
	 * @see #renderMergedOutputModel
	 */
	public void render(Map model, HttpServletRequest request, HttpServletResponse response) throws Exception {
		if (logger.isDebugEnabled()) {
			logger.debug("Rendering view with name '" + this.beanName + "' with model " + model +
				" and static attributes " + this.staticAttributes);
		}

		// Consolidate static and dynamic model attributes.
		Map mergedModel = new HashMap(this.staticAttributes.size() + (model != null ? model.size() : 0));
		mergedModel.putAll(this.staticAttributes);
		if (model != null) {
			mergedModel.putAll(model);
		}

		// Expose RequestContext?
		if (this.requestContextAttribute != null) {
			mergedModel.put(this.requestContextAttribute, createRequestContext(request, mergedModel));
		}

		prepareResponse(request, response);
		renderMergedOutputModel(mergedModel, request, response);
	}

	/**
	 * Create a RequestContext to expose under the specified attribute name.
	 * <p>Default implementation creates a standard RequestContext instance for the
	 * given request and model. Can be overridden in subclasses for custom instances.
	 * @param request current HTTP request
	 * @param model combined output Map (never <code>null),
	 * with dynamic values taking precedence over static attributes
	 * @return the RequestContext instance
	 * @see #setRequestContextAttribute
	 * @see org.springframework.web.servlet.support.RequestContext
	 */
	protected RequestContext createRequestContext(HttpServletRequest request, Map model) {
		return new RequestContext(request, getServletContext(), model);
	}

	/**
	 * Prepare the given response for rendering.
	 * <p>The default implementation applies a workaround for an IE bug
	 * when sending download content via HTTPS.
	 * @param request current HTTP request
	 * @param response current HTTP response
	 */
	protected void prepareResponse(HttpServletRequest request, HttpServletResponse response) {
		if (generatesDownloadContent()) {
			response.setHeader("Pragma", "private");
			response.setHeader("Cache-Control", "private, must-revalidate");
		}
	}

	/**
	 * Return whether this view generates download content
	 * (typically binary content like PDF or Excel files).
	 * <p>The default implementation returns false. Subclasses are
	 * encouraged to return <code>true here if they know that they are
	 * generating download content that requires temporary caching on the
	 * client side, typically via the response OutputStream.
	 * @see #prepareResponse
	 * @see javax.servlet.http.HttpServletResponse#getOutputStream()
	 */
	protected boolean generatesDownloadContent() {
		return false;
	}

	/**
	 * Subclasses must implement this method to actually render the view.
	 * <p>The first step will be preparing the request: In the JSP case,
	 * this would mean setting model objects as request attributes.
	 * The second step will be the actual rendering of the view,
	 * for example including the JSP via a RequestDispatcher.
	 * @param model combined output Map (never <code>null),
	 * with dynamic values taking precedence over static attributes
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @throws Exception if rendering failed
	 */
	protected abstract void renderMergedOutputModel(
			Map model, HttpServletRequest request, HttpServletResponse response) throws Exception;


	/**
	 * Expose the model objects in the given map as request attributes.
	 * Names will be taken from the model Map.
	 * This method is suitable for all resources reachable by {@link javax.servlet.RequestDispatcher}.
	 * @param model Map of model objects to expose
	 * @param request current HTTP request
	 */
	protected void exposeModelAsRequestAttributes(Map model, HttpServletRequest request) throws Exception {
		Iterator it = model.entrySet().iterator();
		while (it.hasNext()) {
			Map.Entry entry = (Map.Entry) it.next();
			if (!(entry.getKey() instanceof String)) {
				throw new IllegalArgumentException(
						"Invalid key [" + entry.getKey() + "] in model Map: only Strings allowed as model keys");
			}
			String modelName = (String) entry.getKey();
			Object modelValue = entry.getValue();
			if (modelValue != null) {
				request.setAttribute(modelName, modelValue);
				if (logger.isDebugEnabled()) {
					logger.debug("Added model object '" + modelName + "' of type [" + modelValue.getClass().getName() +
							"] to request in view with name '" + getBeanName() + "'");
				}
			}
			else {
				request.removeAttribute(modelName);
				if (logger.isDebugEnabled()) {
					logger.debug("Removed model object '" + modelName +
							"' from request in view with name '" + getBeanName() + "'");
				}
			}
		}
	}


	public String toString() {
		StringBuffer sb = new StringBuffer(getClass().getName());
		if (getBeanName() != null) {
			sb.append(": name '").append(getBeanName()).append("'");
		}
		else {
			sb.append(": unnamed");
		}
		return sb.toString();
	}

}

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