/*
* Copyright 2002-2009 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.HashMap;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;
import org.springframework.beans.BeanUtils;
import org.springframework.core.Ordered;
import org.springframework.util.CollectionUtils;
import org.springframework.util.PatternMatchUtils;
import org.springframework.web.servlet.View;
/**
* Simple implementation of the {@link org.springframework.web.servlet.ViewResolver}
* interface, allowing for direct resolution of symbolic view names to URLs,
* without explicit mapping definition. This is useful if your symbolic names
* match the names of your view resources in a straightforward manner
* (i.e. the symbolic name is the unique part of the resource's filename),
* without the need for a dedicated mapping to be defined for each view.
*
* <p>Supports {@link AbstractUrlBasedView} subclasses like {@link InternalResourceView},
* {@link org.springframework.web.servlet.view.velocity.VelocityView} and
* {@link org.springframework.web.servlet.view.freemarker.FreeMarkerView}.
* The view class for all views generated by this resolver can be specified
* via the "viewClass" property.
*
* <p>View names can either be resource URLs themselves, or get augmented by a
* specified prefix and/or suffix. Exporting an attribute that holds the
* RequestContext to all views is explicitly supported.
*
* <p>Example: prefix="/WEB-INF/jsp/", suffix=".jsp", viewname="test" ->
* "/WEB-INF/jsp/test.jsp"
*
* <p>As a special feature, redirect URLs can be specified via the "redirect:"
* prefix. E.g.: "redirect:myAction.do" will trigger a redirect to the given
* URL, rather than resolution as standard view name. This is typically used
* for redirecting to a controller URL after finishing a form workflow.
*
* <p>Furthermore, forward URLs can be specified via the "forward:" prefix. E.g.:
* "forward:myAction.do" will trigger a forward to the given URL, rather than
* resolution as standard view name. This is typically used for controller URLs;
* it is not supposed to be used for JSP URLs - use logical view names there.
*
* <p>Note: This class does not support localized resolution, i.e. resolving
* a symbolic view name to different resources depending on the current locale.
*
* <p><b>Note:</b> When chaining ViewResolvers, a UrlBasedViewResolver will check whether
* the {@link AbstractUrlBasedView#checkResource specified resource actually exists}.
* However, with {@link InternalResourceView}, it is not generally possible to
* determine the existence of the target resource upfront. In such a scenario,
* a UrlBasedViewResolver will always return View for any given view name;
* as a consequence, it should be configured as the last ViewResolver in the chain.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @since 13.12.2003
* @see #setViewClass
* @see #setPrefix
* @see #setSuffix
* @see #setRequestContextAttribute
* @see #REDIRECT_URL_PREFIX
* @see AbstractUrlBasedView
* @see InternalResourceView
* @see org.springframework.web.servlet.view.velocity.VelocityView
* @see org.springframework.web.servlet.view.freemarker.FreeMarkerView
*/
public class UrlBasedViewResolver extends AbstractCachingViewResolver implements Ordered {
/**
* Prefix for special view names that specify a redirect URL (usually
* to a controller after a form has been submitted and processed).
* Such view names will not be resolved in the configured default
* way but rather be treated as special shortcut.
*/
public static final String REDIRECT_URL_PREFIX = "redirect:";
/**
* Prefix for special view names that specify a forward URL (usually
* to a controller after a form has been submitted and processed).
* Such view names will not be resolved in the configured default
* way but rather be treated as special shortcut.
*/
public static final String FORWARD_URL_PREFIX = "forward:";
private Class viewClass;
private String prefix = "";
private String suffix = "";
private String[] viewNames = null;
private String contentType;
private boolean redirectContextRelative = true;
private boolean redirectHttp10Compatible = true;
private String requestContextAttribute;
private int order = Integer.MAX_VALUE;
/** Map of static attributes, keyed by attribute name (String) */
private final Map<String, Object> staticAttributes = new HashMap<String, Object>();
/**
* Set the view class that should be used to create views.
* @param viewClass class that is assignable to the required view class
* (by default, AbstractUrlBasedView)
* @see AbstractUrlBasedView
*/
public void setViewClass(Class viewClass) {
if (viewClass == null || !requiredViewClass().isAssignableFrom(viewClass)) {
throw new IllegalArgumentException(
"Given view class [" + (viewClass != null ? viewClass.getName() : null) +
"] is not of type [" + requiredViewClass().getName() + "]");
}
this.viewClass = viewClass;
}
/**
* Return the view class to be used to create views.
*/
protected Class getViewClass() {
return this.viewClass;
}
/**
* Return the required type of view for this resolver.
* This implementation returns AbstractUrlBasedView.
* @see AbstractUrlBasedView
*/
protected Class requiredViewClass() {
return AbstractUrlBasedView.class;
}
/**
* Set the prefix that gets prepended to view names when building a URL.
*/
public void setPrefix(String prefix) {
this.prefix = (prefix != null ? prefix : "");
}
/**
* Return the prefix that gets prepended to view names when building a URL.
*/
protected String getPrefix() {
return this.prefix;
}
/**
* Set the suffix that gets appended to view names when building a URL.
*/
public void setSuffix(String suffix) {
this.suffix = (suffix != null ? suffix : "");
}
/**
* Return the suffix that gets appended to view names when building a URL.
*/
protected String getSuffix() {
return this.suffix;
}
/**
* Set the content type for all views.
* <p>May be ignored by view classes 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 all views, if any.
*/
protected String getContentType() {
return this.contentType;
}
/**
* Set whether to interpret a given redirect URL that starts with a
* slash ("/") as relative to the current ServletContext, i.e. as
* relative to the web application root.
* <p>Default is "true": A redirect URL that starts with a slash will be
* interpreted as relative to the web application root, i.e. the context
* path will be prepended to the URL.
* <p><b>Redirect URLs can be specified via the "redirect:" prefix.</b>
* E.g.: "redirect:myAction.do"
* @see RedirectView#setContextRelative
* @see #REDIRECT_URL_PREFIX
*/
public void setRedirectContextRelative(boolean redirectContextRelative) {
this.redirectContextRelative = redirectContextRelative;
}
/**
* Return whether to interpret a given redirect URL that starts with a
* slash ("/") as relative to the current ServletContext, i.e. as
* relative to the web application root.
*/
protected boolean isRedirectContextRelative() {
return this.redirectContextRelative;
}
/**
* Set whether redirects should stay compatible with HTTP 1.0 clients.
* <p>In the default implementation, this will enforce HTTP status code 302
* in any case, i.e. delegate to <code>HttpServletResponse.sendRedirect</code>.
* Turning this off will send HTTP status code 303, which is the correct
* code for HTTP 1.1 clients, but not understood by HTTP 1.0 clients.
* <p>Many HTTP 1.1 clients treat 302 just like 303, not making any
* difference. However, some clients depend on 303 when redirecting
* after a POST request; turn this flag off in such a scenario.
* <p><b>Redirect URLs can be specified via the "redirect:" prefix.</b>
* E.g.: "redirect:myAction.do"
* @see RedirectView#setHttp10Compatible
* @see #REDIRECT_URL_PREFIX
*/
public void setRedirectHttp10Compatible(boolean redirectHttp10Compatible) {
this.redirectHttp10Compatible = redirectHttp10Compatible;
}
/**
* Return whether redirects should stay compatible with HTTP 1.0 clients.
*/
protected boolean isRedirectHttp10Compatible() {
return this.redirectHttp10Compatible;
}
/**
* Set the name of the RequestContext attribute for all views.
* @param requestContextAttribute name of the RequestContext attribute
* @see AbstractView#setRequestContextAttribute
*/
public void setRequestContextAttribute(String requestContextAttribute) {
this.requestContextAttribute = requestContextAttribute;
}
/**
* Return the name of the RequestContext attribute for all views, if any.
*/
protected String getRequestContextAttribute() {
return this.requestContextAttribute;
}
/**
* Set static attributes from a <code>java.util.Properties</code> object,
* for all views returned by this resolver.
* <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
* @see AbstractView#setAttributes
*/
public void setAttributes(Properties props) {
CollectionUtils.mergePropertiesIntoMap(props, this.staticAttributes);
}
/**
* Set static attributes from a Map, for all views returned by this resolver.
* This allows to set any kind of attribute values, for example bean references.
* <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
* @see AbstractView#setAttributesMap
*/
public void setAttributesMap(Map<String, ?> attributes) {
if (attributes != null) {
this.staticAttributes.putAll(attributes);
}
}
/**
* Allow Map access to the static attributes for views returned by
* this resolver, 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<String, Object> getAttributesMap() {
return this.staticAttributes;
}
/**
* Set the view names (or name patterns) that can be handled by this
* {@link org.springframework.web.servlet.ViewResolver}. View names can contain
* simple wildcards such that 'my*', '*Report' and '*Repo*' will all match the
* view name 'myReport'.
* @see #canHandle
*/
public void setViewNames(String[] viewNames) {
this.viewNames = viewNames;
}
/**
* Return the view names (or name patterns) that can be handled by this
* {@link org.springframework.web.servlet.ViewResolver}.
*/
protected String[] getViewNames() {
return this.viewNames;
}
/**
* Set the order in which this {@link org.springframework.web.servlet.ViewResolver}
* is evaluated.
*/
public void setOrder(int order) {
this.order = order;
}
/**
* Return the order in which this {@link org.springframework.web.servlet.ViewResolver}
* is evaluated.
*/
public int getOrder() {
return this.order;
}
@Override
protected void initApplicationContext() {
super.initApplicationContext();
if (getViewClass() == null) {
throw new IllegalArgumentException("Property 'viewClass' is required");
}
}
/**
* This implementation returns just the view name,
* as this ViewResolver doesn't support localized resolution.
*/
@Override
protected Object getCacheKey(String viewName, Locale locale) {
return viewName;
}
/**
* Overridden to implement check for "redirect:" prefix.
* <p>Not possible in <code>loadView</code>, since overridden
* <code>loadView</code> versions in subclasses might rely on the
* superclass always creating instances of the required view class.
* @see #loadView
* @see #requiredViewClass
*/
@Override
protected View createView(String viewName, Locale locale) throws Exception {
// If this resolver is not supposed to handle the given view,
// return null to pass on to the next resolver in the chain.
if (!canHandle(viewName, locale)) {
return null;
}
// Check for special "redirect:" prefix.
if (viewName.startsWith(REDIRECT_URL_PREFIX)) {
String redirectUrl = viewName.substring(REDIRECT_URL_PREFIX.length());
return new RedirectView(redirectUrl, isRedirectContextRelative(), isRedirectHttp10Compatible());
}
// Check for special "forward:" prefix.
if (viewName.startsWith(FORWARD_URL_PREFIX)) {
String forwardUrl = viewName.substring(FORWARD_URL_PREFIX.length());
return new InternalResourceView(forwardUrl);
}
// Else fall back to superclass implementation: calling loadView.
return super.createView(viewName, locale);
}
/**
* Indicates whether or not this {@link org.springframework.web.servlet.ViewResolver} can
* handle the supplied view name. If not, {@link #createView(String, java.util.Locale)} will
* return <code>null</code>. The default implementation checks against the configured
* {@link #setViewNames view names}.
* @param viewName the name of the view to retrieve
* @param locale the Locale to retrieve the view for
* @return whether this resolver applies to the specified view
* @see org.springframework.util.PatternMatchUtils#simpleMatch(String, String)
*/
protected boolean canHandle(String viewName, Locale locale) {
String[] viewNames = getViewNames();
return (viewNames == null || PatternMatchUtils.simpleMatch(viewNames, viewName));
}
/**
* Delegates to <code>buildView</code> for creating a new instance of the
* specified view class, and applies the following Spring lifecycle methods
* (as supported by the generic Spring bean factory):
* <ul>
* <li>ApplicationContextAware's <code>setApplicationContext</code>
* <li>InitializingBean's <code>afterPropertiesSet</code>
* </ul>
* @param viewName the name of the view to retrieve
* @return the View instance
* @throws Exception if the view couldn't be resolved
* @see #buildView(String)
* @see org.springframework.context.ApplicationContextAware#setApplicationContext
* @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet
*/
@Override
protected View loadView(String viewName, Locale locale) throws Exception {
AbstractUrlBasedView view = buildView(viewName);
View result = (View) getApplicationContext().getAutowireCapableBeanFactory().initializeBean(view, viewName);
return (view.checkResource(locale) ? result : null);
}
/**
* Creates a new View instance of the specified view class and configures it.
* Does <i>not</i> perform any lookup for pre-defined View instances.
* <p>Spring lifecycle methods as defined by the bean container do not have to
* be called here; those will be applied by the <code>loadView</code> method
* after this method returns.
* <p>Subclasses will typically call <code>super.buildView(viewName)</code>
* first, before setting further properties themselves. <code>loadView</code>
* will then apply Spring lifecycle methods at the end of this process.
* @param viewName the name of the view to build
* @return the View instance
* @throws Exception if the view couldn't be resolved
* @see #loadView(String, java.util.Locale)
*/
protected AbstractUrlBasedView buildView(String viewName) throws Exception {
AbstractUrlBasedView view = (AbstractUrlBasedView) BeanUtils.instantiateClass(getViewClass());
view.setUrl(getPrefix() + viewName + getSuffix());
String contentType = getContentType();
if (contentType != null) {
view.setContentType(contentType);
}
view.setRequestContextAttribute(getRequestContextAttribute());
view.setAttributesMap(getAttributesMap());
return view;
}
}
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