/*
* Copyright 2002-2006 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.mvc.multiaction;
import java.util.Properties;
import javax.servlet.http.HttpServletRequest;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
import org.springframework.web.util.WebUtils;
/**
* Implementation of MethodNameResolver which supports several strategies for
* mapping parameter values to the names of methods to invoke.
*
* <p>The simplest strategy looks for a specific named parameter, whose value is
* considered the name of the method to invoke. The name of the parameter may be
* specified as a JavaBean property, if the default <code>action</code> is not
* acceptable.
*
* <p>The alternative strategy uses the very existence of a request parameter (
* i.e. a request parameter with a certain name is found) as an indication that a
* method with the same name should be dispatched to. In this case, the actual
* request parameter value is ignored. The list of parameter/method names may
* be set via the <code>methodParamNames<code> JavaBean property.
*
* <p>The second resolution strategy is primarily expected to be used with web
* pages containing multiple submit buttons. The 'name' attribute of each
* button should be set to the mapped method name, while the 'value' attribute
* is normally displayed as the button label by the browser, and will be
* ignored by the resolver.
*
* <p>Note that the second strategy also supports the use of submit buttons of
* type 'image'. That is, an image submit button named 'reset' will normally be
* submitted by the browser as two request paramters called 'reset.x', and
* 'reset.y'. When checking for the existence of a paramter from the
* <code>methodParamNames</code> list, to indicate that a specific method should
* be called, the code will look for request parameter in the "reset" form
* (exactly as spcified in the list), and in the "reset.x" form ('.x' appended to
* the name in the list). In this way it can handle both normal and image submit
* buttons. The actual method name resolved if there is a match will always be
* the bare form without the ".x".
*
* <p><b>Note:</b> If both strategies are configured, i.e. both "paramName"
* and "methodParamNames" are specified, then both will be checked for any given
* request. A match for an explicit request parameter in the "methodParamNames"
* list always wins over a value specified for a "paramName" action parameter.
*
* <p>For use with either strategy, the name of a default handler method to use
* when there is no match, can be specified as a JavaBean property.
*
* <p>For both resolution strategies, the method name is of course coming from
* some sort of view code, (such as a JSP page). While this may be acceptable,
* it is sometimes desireable to treat this only as a 'logical' method name,
* with a further mapping to a 'real' method name. As such, an optional
* 'logical' mapping may be specified for this purpose.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @author Colin Sampaleanu
* @see #setParamName
* @see #setMethodParamNames
* @see #setLogicalMappings
* @see #setDefaultMethodName
*/
public class ParameterMethodNameResolver implements MethodNameResolver {
/**
* Default name for the parameter whose value identifies the method to invoke:
* "action".
*/
public static final String DEFAULT_PARAM_NAME = "action";
protected final Log logger = LogFactory.getLog(getClass());
private String paramName = DEFAULT_PARAM_NAME;
private String[] methodParamNames;
private Properties logicalMappings;
private String defaultMethodName;
/**
* Set the name of the parameter whose <i>value</i> identifies the name of
* the method to invoke. Default is "action".
* <p>Alternatively, specify parameter names where the very existence of each
* parameter means that a method of the same name should be invoked, via
* the "methodParamNames" property.
* @see #setMethodParamNames
*/
public void setParamName(String paramName) {
if (paramName != null) {
Assert.hasText(paramName, "'paramName' must not be empty");
}
this.paramName = paramName;
}
/**
* Set a String array of parameter names, where the <i>very existence of a
* parameter</i> in the list (with value ignored) means that a method of the
* same name should be invoked. This target method name may then be optionally
* further mapped via the {@link #logicalMappings} property, in which case it
* can be considered a logical name only.
* @see #setParamName
*/
public void setMethodParamNames(String[] methodParamNames) {
this.methodParamNames = methodParamNames;
}
/**
* Specifies a set of optional logical method name mappings. For both resolution
* strategies, the method name initially comes in from the view layer. If that needs
* to be treated as a 'logical' method name, and mapped to a 'real' method name, then
* a name/value pair for that purpose should be added to this Properties instance.
* Any method name not found in this mapping will be considered to already be the
* real method name.
* <p>Note that in the case of no match, where the {@link #defaultMethodName} property
* is used if available, that method name is considered to already be the real method
* name, and is not run through the logical mapping.
* @param logicalMappings a Properties object mapping logical method names to real
* method names
*/
public void setLogicalMappings(Properties logicalMappings) {
this.logicalMappings = logicalMappings;
}
/**
* Set the name of the default handler method that should be
* used when no parameter was found in the request
*/
public void setDefaultMethodName(String defaultMethodName) {
if (defaultMethodName != null) {
Assert.hasText(defaultMethodName, "'defaultMethodName' must not be empty");
}
this.defaultMethodName = defaultMethodName;
}
public String getHandlerMethodName(HttpServletRequest request) throws NoSuchRequestHandlingMethodException {
String methodName = null;
// Check parameter names where the very existence of each parameter
// means that a method of the same name should be invoked, if any.
if (this.methodParamNames != null) {
for (int i = 0; i < this.methodParamNames.length; ++i) {
String candidate = this.methodParamNames[i];
if (WebUtils.hasSubmitParameter(request, candidate)) {
methodName = candidate;
if (logger.isDebugEnabled()) {
logger.debug("Determined handler method '" + methodName +
"' based on existence of explicit request parameter of same name");
}
break;
}
}
}
// Check parameter whose value identifies the method to invoke, if any.
if (methodName == null && this.paramName != null) {
methodName = request.getParameter(this.paramName);
if (methodName != null) {
if (logger.isDebugEnabled()) {
logger.debug("Determined handler method '" + methodName +
"' based on value of request parameter '" + this.paramName + "'");
}
}
}
if (methodName != null && this.logicalMappings != null) {
// Resolve logical name into real method name, if appropriate.
String originalName = methodName;
methodName = this.logicalMappings.getProperty(methodName, methodName);
if (logger.isDebugEnabled()) {
logger.debug("Resolved method name '" + originalName + "' to handler method '" + methodName + "'");
}
}
if (methodName != null && !StringUtils.hasText(methodName)) {
if (logger.isDebugEnabled()) {
logger.debug("Method name '" + methodName + "' is empty: treating it as no method name found");
}
methodName = null;
}
if (methodName == null) {
if (this.defaultMethodName != null) {
// No specific method resolved: use default method.
methodName = this.defaultMethodName;
if (logger.isDebugEnabled()) {
logger.debug("Falling back to default handler method '" + this.defaultMethodName + "'");
}
}
else {
// If resolution failed completely, throw an exception.
throw new NoSuchRequestHandlingMethodException(request);
}
}
return methodName;
}
}