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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript.
It gets rid of almost all the boiler plate code between the web browser and your Java code.
/*
* Copyright 2005 Joe Walker
*
* 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.directwebremoting.dwrp;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.directwebremoting.extend.Converter;
import org.directwebremoting.extend.ConverterManager;
import org.directwebremoting.extend.InboundContext;
import org.directwebremoting.extend.InboundVariable;
import org.directwebremoting.extend.MarshallException;
import org.directwebremoting.extend.NamedConverter;
import org.directwebremoting.extend.OutboundContext;
import org.directwebremoting.extend.OutboundVariable;
import org.directwebremoting.extend.TypeHintContext;
import org.directwebremoting.util.LocalUtil;
import org.directwebremoting.util.Logger;
import org.directwebremoting.util.Messages;
/**
* A class to manage the converter types and the instansiated class name matches.
* @author Joe Walker [joe at getahead dot ltd dot uk]
*/
public class DefaultConverterManager implements ConverterManager
{
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#addConverterType(java.lang.String, java.lang.String)
*/
public void addConverterType(String id, String className)
{
if (!LocalUtil.isJavaIdentifier(id))
{
log.error("Illegal identifier: '" + id + "'");
return;
}
Class clazz = LocalUtil.classForName(id, className, Converter.class);
if (clazz != null)
{
log.debug("- adding converter type: " + id + " = " + clazz.getName());
converterTypes.put(id, clazz);
}
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#addConverter(java.lang.String, java.lang.String, java.util.Map)
*/
public void addConverter(String match, String type, Map params) throws IllegalArgumentException, InstantiationException, IllegalAccessException
{
Class clazz = (Class) converterTypes.get(type);
if (clazz == null)
{
log.info("Probably not an issue: " + match + " is not available so the " + type + " converter will not load. This is only an problem if you wanted to use it.");
return;
}
Converter converter = (Converter) clazz.newInstance();
converter.setConverterManager(this);
LocalUtil.setParams(converter, params, ignore);
// add the converter for the specified match
addConverter(match, converter);
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#addConverter(java.lang.String, org.directwebremoting.Converter)
*/
public void addConverter(String match, Converter converter) throws IllegalArgumentException
{
// Check that we don't have this one already
Converter other = (Converter) converters.get(match);
if (other != null)
{
log.warn("Clash of converters for " + match + ". Using " + converter.getClass().getName() + " in place of " + other.getClass().getName());
}
log.debug("- adding converter: " + LocalUtil.getShortClassName(converter.getClass()) + " for " + match);
converters.put(match, converter);
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#getConverterMatchStrings()
*/
public Collection getConverterMatchStrings()
{
return Collections.unmodifiableSet(converters.keySet());
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#getConverterByMatchString(java.lang.String)
*/
public Converter getConverterByMatchString(String match)
{
return (Converter) converters.get(match);
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#isConvertable(java.lang.Class)
*/
public boolean isConvertable(Class paramType)
{
return getConverter(paramType) != null;
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#convertInbound(java.lang.Class, org.directwebremoting.InboundVariable, org.directwebremoting.InboundContext, org.directwebremoting.TypeHintContext)
*/
public Object convertInbound(Class paramType, InboundVariable iv, InboundContext inctx, TypeHintContext incc) throws MarshallException
{
Object converted = inctx.getConverted(iv, paramType);
if (converted == null)
{
// Was the inbound variable marshalled as an Object in the client
// (could mean that this is an instance of one of our generated
// JavaScript classes)
Converter converter = getNamedConverter(paramType, iv.getType());
// Fall back to the standard way of locating a converter if we
// didn't find anything above
if (converter == null)
{
converter = getConverter(paramType);
}
if (converter == null)
{
throw new MarshallException(paramType, Messages.getString("DefaultConverterManager.MissingConverter", paramType));
}
// We only think about doing a null conversion ourselves once we are
// sure that there is a converter available. This prevents hackers
// from passing null to things they are not allowed to convert
if (iv.isNull())
{
return null;
}
inctx.pushContext(incc);
converted = converter.convertInbound(paramType, iv, inctx);
inctx.popContext();
}
return converted;
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#convertOutbound(java.lang.Object, org.directwebremoting.OutboundContext)
*/
public OutboundVariable convertOutbound(Object object, OutboundContext outctx) throws MarshallException
{
if (object == null)
{
return new SimpleOutboundVariable("null", outctx, true);
}
// Check to see if we have done this one already
OutboundVariable ov = outctx.get(object);
if (ov != null)
{
// So the object as been converted already, we just need to refer to it.
return ov.getReferenceVariable();
}
// So we will have to do the conversion
Converter converter = getConverter(object);
if (converter == null)
{
log.error(Messages.getString("DefaultConverterManager.MissingConverter", object.getClass().getName()));
return new SimpleOutboundVariable("null", outctx, true);
}
return converter.convertOutbound(object, outctx);
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#setExtraTypeInfo(org.directwebremoting.TypeHintContext, java.lang.Class)
*/
public void setExtraTypeInfo(TypeHintContext thc, Class type)
{
extraTypeInfoMap.put(thc, type);
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#getExtraTypeInfo(org.directwebremoting.TypeHintContext)
*/
public Class getExtraTypeInfo(TypeHintContext thc)
{
Class type = (Class) extraTypeInfoMap.get(thc);
return type;
}
/* (non-Javadoc)
* @see org.directwebremoting.ConverterManager#setConverters(java.util.Map)
*/
public void setConverters(Map converters)
{
this.converters = converters;
}
/**
* Like getConverter(object.getClass()); except that since the
* object can be null we check for that fist and then do a lookup against
* the Void.TYPE converter
* @param object The object to find a converter for
* @return The converter for the given type
*/
private Converter getConverter(Object object)
{
if (object == null)
{
return getConverter(Void.TYPE);
}
return getConverter(object.getClass());
}
/**
* When we are using typed Javascript names we sometimes want to get a
* specially named converter
* @param paramType The class that we are converting to
* @param type The type name as passed in from the client
* @return The Converter that matches this request (if any)
* @throws MarshallException
*/
protected Converter getNamedConverter(Class paramType, String type) throws MarshallException
{
if (type.startsWith("Object_"))
{
// Extract the JavaScript classname from the inbound type
String javascriptClassName = type.substring("Object_".length());
// Locate a converter for this JavaScript classname
Iterator it = converters.entrySet().iterator();
while (it.hasNext())
{
Map.Entry entry = (Map.Entry) it.next();
String match = (String) entry.getKey();
Converter conv = (Converter) entry.getValue();
// JavaScript mapping is only applicable for compound converters
if (conv instanceof NamedConverter)
{
NamedConverter boConv = (NamedConverter) conv;
if (boConv.getJavascript() != null && boConv.getJavascript().equals(javascriptClassName))
{
// We found a potential converter! But is the
// converter's Java class compatible with the
// parameter type?
try
{
Class inboundClass = LocalUtil.classForName(match);
if (paramType.isAssignableFrom(inboundClass))
{
// Hack: We also want to make sure that the
// converter creates its object based on the
// inbound class instead of the parameter
// type, and we have to use the other ref
// for this:
boConv.setInstanceType(inboundClass);
return boConv;
}
}
catch (ClassNotFoundException ex)
{
throw new MarshallException(paramType, ex);
}
}
}
}
}
return null;
}
/**
* @param paramType The type to find a converter for
* @return The converter for the given type, or null if one can't be found
*/
private Converter getConverter(Class paramType)
{
// Can we find a converter assignable to paramType in the HashMap?
Converter converter = getConverterAssignableFrom(paramType);
if (converter != null)
{
return converter;
}
String lookup = paramType.getName();
// Before we start trying for a match on package parts we check for
// dynamic proxies
if (lookup.startsWith("$Proxy"))
{
converter = (Converter) converters.get("$Proxy*");
if (converter != null)
{
return converter;
}
}
while (true)
{
// Can we find a converter using wildcards?
converter = (Converter) converters.get(lookup + ".*");
if (converter != null)
{
return converter;
}
// Arrays can have wildcards like [L* so we don't require a '.'
converter = (Converter) converters.get(lookup + '*');
if (converter != null)
{
return converter;
}
// Give up if the name is now empty
if (lookup.length() == 0)
{
break;
}
// Strip of the component after the last .
int lastdot = lookup.lastIndexOf('.');
if (lastdot != -1)
{
lookup = lookup.substring(0, lastdot);
}
else
{
int arrayMarkers = 0;
while (lookup.charAt(arrayMarkers) == '[')
{
arrayMarkers++;
}
if (arrayMarkers == 0)
{
// so we are out of dots and out of array markers
// bail out.
break;
}
// We want to keep the type marker too
lookup = lookup.substring(arrayMarkers - 1, arrayMarkers + 1);
// Now can we find it?
converter = (Converter) converters.get(lookup);
if (converter != null)
{
return converter;
}
}
}
return null;
}
/**
* @param paramType The type to find a converter for
* @return The converter assignable for the given type, or null if one can't be found
*/
private Converter getConverterAssignableFrom(Class paramType)
{
if (paramType == null)
{
return null;
}
String lookup = paramType.getName();
// Can we find the converter for paramType in the converters HashMap?
Converter converter = (Converter) converters.get(lookup);
if (converter != null)
{
return converter;
}
// Lookup all of the interfaces of this class for a match
Class[] interfaces = paramType.getInterfaces();
for (int i = 0; i < interfaces.length; i++)
{
converter = getConverterAssignableFrom(interfaces[i]);
if (converter != null)
{
converters.put(lookup, converter);
return converter;
}
}
// Let's search it in paramType superClass
converter = getConverterAssignableFrom(paramType.getSuperclass());
if (converter != null)
{
converters.put(lookup, converter);
}
return converter;
}
/**
* Where we store real type information behind generic types
*/
private Map extraTypeInfoMap = new HashMap();
/**
* The log stream
*/
private static final Logger log = Logger.getLogger(DefaultConverterManager.class);
/**
* The list of the available converters
*/
private Map converterTypes = new HashMap();
/**
* The list of the configured converters
*/
private Map converters = new HashMap();
/**
* The properties that we don't warn about if they don't exist.
* @see DefaultConverterManager#addConverter(String, String, Map)
*/
private static List ignore = Arrays.asList(new String[] { "converter", "match" });
}
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