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2010-06-01T07:07:19Z

1 версия

в 18:01, 31 мая 2010

2010-05-31T18:01:46Z

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== A simple demonstration of how the event handling features of the Velocity Servlet Engine are used ==



<source lang="java">
/*
* Copyright 2001,2004 The Apache Software Foundation.
*
* 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.
*/
import java.io.StringWriter;
import java.util.Properties;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.runtime.log.LogSystem;
import org.apache.velocity.runtime.RuntimeServices;
import org.apache.velocity.app.event.EventCartridge;
import org.apache.velocity.app.event.ReferenceInsertionEventHandler;
import org.apache.velocity.app.event.MethodExceptionEventHandler;
import org.apache.velocity.app.event.NullSetEventHandler;
import org.apache.velocity.context.Context;
/**
* This class is a simple demonstration of how the event handling
* features of the Velocity Servlet Engine are used. It uses a
* custom logger as well to check the log message stream
* when testing the NullSetEventHandler
*
* @author

== Event Handler: Exceptions ==



<source lang="java">
import java.io.StringWriter;
import java.io.Writer;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.app.event.EventCartridge;
import org.apache.velocity.app.event.MethodExceptionEventHandler;
import org.apache.velocity.app.event.NullSetEventHandler;
import org.apache.velocity.app.event.ReferenceInsertionEventHandler;
import org.apache.velocity.context.Context;
public class EventHandler implements ReferenceInsertionEventHandler,
NullSetEventHandler, MethodExceptionEventHandler {
public EventHandler(Context ctx) {
EventCartridge ec = new EventCartridge();
ec.addEventHandler(this);
ec.attachToContext(ctx);
}
public Object referenceInsert(String reference, Object data) {
System.out.println("referenceInsert: " + reference + " data: " + data);
return data;
}
public boolean shouldLogOnNullSet(String lhs, String rhs) {
System.out.println("shouldLogOnNullSet");
System.out.println("lhs:" + lhs + " rhs:" + rhs);
return true;
}
public Object methodException(Class cls, String method, Exception e)
throws Exception {
return "An " + e.getClass().getName() + " was thrown by the " + method
+ " method of the " + cls.getName() + " class [" + e.getMessage() + "]";
}
public static void main(String[] args) throws Exception {
Velocity.init();
Template t = Velocity.getTemplate("./src/eventHandler.vm");
Context ctx = new VelocityContext();
ctx.put("person", "Joe");
ctx.put("exception", new ExceptionGenerator());
EventHandler hdl = new EventHandler(ctx);
Writer writer = new StringWriter();
t.merge(ctx, writer);
System.out.println(writer);
}
}

import java.util.Random;
public class ExceptionGenerator {
public String generate() throws Exception {
Random rnd = new Random();
int x = rnd.nextInt(5);
if (x == 2) {
throw new Exception("Unlucky!");
} else {
return "No Exception";
}
}
}
-------------------------------------------------------------------------------------
#set($myNull1 = $validNull)
#set($myNull2 = $invalidNull)
This is $person
$exception.generate()
$exception.generate()
$exception.generate()
$exception.generate()

</source>

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Admin: 1 версия

в 18:01, 31 мая 2010