package org.apache.velocity;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.util.List;
import org.apache.velocity.context.Context;
import org.apache.velocity.context.InternalContextAdapterImpl;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.exception.TemplateInitException;
import org.apache.velocity.exception.VelocityException;
import org.apache.velocity.runtime.parser.ParseException;
import org.apache.velocity.runtime.parser.node.SimpleNode;
import org.apache.velocity.runtime.resource.Resource;
import org.apache.velocity.runtime.resource.ResourceManager;
/**
* This class is used for controlling all template
* operations. This class uses a parser created
* by JavaCC to create an AST that is subsequently
* traversed by a Visitor.
*
* <pre>
* // set up and initialize Velocity before this code block
*
* Template template = Velocity.getTemplate("test.wm");
* Context context = new VelocityContext();
*
* context.put("foo", "bar");
* context.put("customer", new Customer());
*
* template.merge(context, writer);
* </pre>
*
* @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
* @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
* @version $Id: Template.java 685724 2008-08-13 23:12:12Z nbubna $
*/
//第一步:
//在Velocity.getTemplate时会调用process()，
//然后在process()过程中生成一棵抽象语法树AST，AST的最顶层的节点是ASTprocess，
//接着调用((SimpleNode)data).init( ica, rsvc);，从顶层的节点开始初始化整棵树.
//第二步:
//调用Template.merge方法，然后( (SimpleNode) data ).render( ica, writer);
//从顶层的节点开始render，结果写入writer中
public class Template extends Resource
{
private static my.Debug DEBUG=new my.Debug(my.Debug.Velocity);//我加上的
private VelocityException errorCondition = null;
/** Default constructor */
public Template()
{
super();
setType(ResourceManager.RESOURCE_TEMPLATE);
}
/**
* gets the named resource as a stream, parses and inits
*
* @return true if successful
* @throws ResourceNotFoundException if template not found
* from any available source.
* @throws ParseErrorException if template cannot be parsed due
* to syntax (or other) error.
* @throws IOException problem reading input stream
*/
public boolean process()
throws ResourceNotFoundException, ParseErrorException, IOException
{
try {//我加上的
DEBUG.P(this,"process()");
data = null;
InputStream is = null;
errorCondition = null;
/*
* first, try to get the stream from the loader
*/
try
{
is = resourceLoader.getResourceStream(name);
}
catch( ResourceNotFoundException rnfe )
{
/*
* remember and re-throw
*/
errorCondition = rnfe;
throw rnfe;
}
/*
* if that worked, lets protect in case a loader impl
* forgets to throw a proper exception
*/
if (is != null)
{
/*
* now parse the template
*/
try
{
BufferedReader br = new BufferedReader( new InputStreamReader( is, encoding ) );
data = rsvc.parse( br, name);
//DEBUG.P("data="+data);
//指:org.apache.velocity.runtime.parser.node.ASTprocess
if(data!=null) DEBUG.P("data.getClass()="+data.getClass());
initDocument();
return true;
}
catch( UnsupportedEncodingException uce )
{
String msg = "Template.process : Unsupported input encoding : " + encoding
+ " for template " + name;
errorCondition = new ParseErrorException( msg );
throw errorCondition;
}
catch ( ParseException pex )
{
/*
* remember the error and convert
*/
errorCondition = new ParseErrorException( pex );
throw errorCondition;
}
catch ( TemplateInitException pex )
{
errorCondition = new ParseErrorException( pex );
throw errorCondition;
}
/**
* pass through runtime exceptions
*/
catch( RuntimeException e )
{
throw new RuntimeException("Exception thrown processing Template "+getName(), e);
}
finally
{
/*
* Make sure to close the inputstream when we are done.
*/
is.close();
}
}
else
{
/*
* is == null, therefore we have some kind of file issue
*/
errorCondition = new ResourceNotFoundException("Unknown resource error for resource " + name );
throw errorCondition;
}
}finally{//我加上的
DEBUG.P(0,this,"process()");
}
}
/**
* initializes the document. init() is not longer
* dependant upon context, but we need to let the
* init() carry the template name down throught for VM
* namespace features
* @throws TemplateInitException When a problem occurs during the document initialization.
*/
public void initDocument()
throws TemplateInitException
{
try {//我加上的
DEBUG.P(this,"initDocument()");
/*
* send an empty InternalContextAdapter down into the AST to initialize it
*/
InternalContextAdapterImpl ica = new InternalContextAdapterImpl( new VelocityContext() );
try
{
/*
* put the current template name on the stack
*/
ica.pushCurrentTemplateName( name );
ica.setCurrentResource( this );
/*
* init the AST
*/
((SimpleNode)data).init( ica, rsvc);
}
finally
{
/*
* in case something blows up...
* pull it off for completeness
*/
ica.popCurrentTemplateName();
ica.setCurrentResource( null );
}
}finally{//我加上的
DEBUG.P(0,this,"initDocument()");
}
}
/**
* The AST node structure is merged with the
* context to produce the final output.
*
* @param context Conext with data elements accessed by template
* @param writer output writer for rendered template
* @throws ResourceNotFoundException if template not found
* from any available source.
* @throws ParseErrorException if template cannot be parsed due
* to syntax (or other) error.
* @throws MethodInvocationException When a method on a referenced object in the context could not invoked.
* @throws IOException Might be thrown while rendering.
*/
public void merge( Context context, Writer writer)
throws ResourceNotFoundException, ParseErrorException, MethodInvocationException, IOException
{
try {//我加上的
DEBUG.P(this,"merge(2)");
merge(context, writer, null);
}finally{//我加上的
DEBUG.P(0,this,"merge(2)");
}
}
/**
* The AST node structure is merged with the
* context to produce the final output.
*
* @param context Conext with data elements accessed by template
* @param writer output writer for rendered template
* @param macroLibraries a list of template files containing macros to be used when merging
* @throws ResourceNotFoundException if template not found
* from any available source.
* @throws ParseErrorException if template cannot be parsed due
* to syntax (or other) error.
* @throws MethodInvocationException When a method on a referenced object in the context could not invoked.
* @throws IOException Might be thrown while rendering.
* @since 1.6
*/
public void merge( Context context, Writer writer, List macroLibraries)
throws ResourceNotFoundException, ParseErrorException, MethodInvocationException, IOException
{
try {//我加上的
DEBUG.P(this,"merge(3)");
/*
* we shouldn't have to do this, as if there is an error condition,
* the application code should never get a reference to the
* Template
*/
if (errorCondition != null)
{
throw errorCondition;
}
if( data != null)
{
/*
* create an InternalContextAdapter to carry the user Context down
* into the rendering engine. Set the template name and render()
*/
InternalContextAdapterImpl ica = new InternalContextAdapterImpl( context );
/**
* Set the macro libraries
*/
ica.setMacroLibraries(macroLibraries);
DEBUG.P("macroLibraries="+macroLibraries);
if (macroLibraries != null)
{
for (int i = 0; i < macroLibraries.size(); i++)
{
/**
* Build the macro library
*/
try
{
rsvc.getTemplate((String) macroLibraries.get(i));
}
catch (ResourceNotFoundException re)
{
/*
* the macro lib wasn't found. Note it and throw
*/
rsvc.getLog().error("template.merge(): " +
"cannot find template " +
(String) macroLibraries.get(i));
throw re;
}
catch (ParseErrorException pe)
{
/*
* the macro lib was found, but didn't parse - syntax error
* note it and throw
*/
rsvc.getLog().error("template.merge(): " +
"syntax error in template " +
(String) macroLibraries.get(i) + ".");
throw pe;
}
catch (Exception e)
{
throw new RuntimeException("Template.merge(): parse failed in template " +
(String) macroLibraries.get(i) + ".", e);
}
}
}
try
{
ica.pushCurrentTemplateName( name );
ica.setCurrentResource( this );
( (SimpleNode) data ).render( ica, writer);
}
finally
{
/*
* lets make sure that we always clean up the context
*/
ica.popCurrentTemplateName();
ica.setCurrentResource( null );
}
}
else
{
/*
* this shouldn't happen either, but just in case.
*/
String msg = "Template.merge() failure. The document is null, " +
"most likely due to parsing error.";
throw new RuntimeException(msg);
}
}finally{//我加上的
DEBUG.P(0,this,"merge(3)");
}
}
}