org.apache.velocity.app.VelocityEngine Maven / Gradle / Ivy
package org.apache.velocity.app;
/*
* 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.Reader;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.util.Properties;
import org.apache.commons.collections.ExtendedProperties;
import org.apache.velocity.Template;
import org.apache.velocity.context.Context;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.RuntimeConstants;
import org.apache.velocity.runtime.RuntimeInstance;
import org.apache.velocity.runtime.log.Log;
/**
*
* This class provides a separate new-able instance of the
* Velocity template engine. The alternative model for use
* is using the Velocity class which employs the singleton
* model.
*
* Velocity will call
* the parameter-less init() at the first use of this class
* if the init() wasn't explicitly called. While this will
* ensure that Velocity functions, it probably won't
* function in the way you intend, so it is strongly recommended that
* you call an init() method yourself if you use the default constructor.
*
*
* @version $Id: VelocityEngine.java 687177 2008-08-19 22:00:32Z nbubna $
*/
public class VelocityEngine implements RuntimeConstants
{
private RuntimeInstance ri = new RuntimeInstance();
/**
* Init-less CTOR
*/
public VelocityEngine()
{
// do nothing
}
/**
* CTOR that invokes an init(String), initializing
* the engine using the properties file specified
*
* @param propsFilename name of properties file to init with
* @throws Exception
* @since 1.5
*/
public VelocityEngine(String propsFilename)
throws Exception
{
ri.init(propsFilename);
}
/**
* CTOR that invokes an init(String), initializing
* the engine using the Properties specified
*
* @param p name of properties to init with
* @throws Exception
* @since 1.5
*/
public VelocityEngine(Properties p)
throws Exception
{
ri.init(p);
}
/**
* initialize the Velocity runtime engine, using the default
* properties of the Velocity distribution
* @throws Exception
*/
public void init()
throws Exception
{
ri.init();
}
/**
* initialize the Velocity runtime engine, using default properties
* plus the properties in the properties file passed in as the arg
*
* @param propsFilename file containing properties to use to initialize
* the Velocity runtime
* @throws Exception
*/
public void init(String propsFilename)
throws Exception
{
ri.init(propsFilename);
}
/**
* initialize the Velocity runtime engine, using default properties
* plus the properties in the passed in java.util.Properties object
*
* @param p Proprties object containing initialization properties
* @throws Exception
*
*/
public void init(Properties p)
throws Exception
{
ri.init(p);
}
/**
* Set a Velocity Runtime property.
*
* @param key
* @param value
*/
public void setProperty(String key, Object value)
{
ri.setProperty(key,value);
}
/**
* Add a Velocity Runtime property.
*
* @param key
* @param value
*/
public void addProperty(String key, Object value)
{
ri.addProperty(key,value);
}
/**
* Clear a Velocity Runtime property.
*
* @param key of property to clear
*/
public void clearProperty(String key)
{
ri.clearProperty(key);
}
/**
* Set an entire configuration at once. This is
* useful in cases where the parent application uses
* the ExtendedProperties class and the velocity configuration
* is a subset of the parent application's configuration.
*
* @param configuration
*
*/
public void setExtendedProperties( ExtendedProperties configuration)
{
ri.setConfiguration( configuration );
}
/**
* Get a Velocity Runtime property.
*
* @param key property to retrieve
* @return property value or null if the property
* not currently set
*/
public Object getProperty( String key )
{
return ri.getProperty( key );
}
/**
* renders the input string using the context into the output writer.
* To be used when a template is dynamically constructed, or want to use
* Velocity as a token replacer.
*
* @param context context to use in rendering input string
* @param out Writer in which to render the output
* @param logTag string to be used as the template name for log
* messages in case of error
* @param instring input string containing the VTL to be rendered
*
* @return true if successful, false otherwise. If false, see
* Velocity runtime log
* @throws ParseErrorException The template could not be parsed.
* @throws MethodInvocationException A method on a context object could not be invoked.
* @throws ResourceNotFoundException A referenced resource could not be loaded.
* @throws IOException While rendering to the writer, an I/O problem occured.
*/
public boolean evaluate( Context context, Writer out,
String logTag, String instring )
throws ParseErrorException, MethodInvocationException,
ResourceNotFoundException, IOException
{
return ri.evaluate(context, out, logTag, instring);
}
/**
* Renders the input stream using the context into the output writer.
* To be used when a template is dynamically constructed, or want to
* use Velocity as a token replacer.
*
* @param context context to use in rendering input string
* @param writer Writer in which to render the output
* @param logTag string to be used as the template name for log messages
* in case of error
* @param instream input stream containing the VTL to be rendered
*
* @return true if successful, false otherwise. If false, see
* Velocity runtime log
* @throws ParseErrorException
* @throws MethodInvocationException
* @throws ResourceNotFoundException
* @throws IOException
* @deprecated Use
* {@link #evaluate( Context context, Writer writer,
* String logTag, Reader reader ) }
*/
public boolean evaluate( Context context, Writer writer,
String logTag, InputStream instream )
throws ParseErrorException, MethodInvocationException,
ResourceNotFoundException, IOException
{
/*
* first, parse - convert ParseException if thrown
*/
BufferedReader br = null;
String encoding = null;
try
{
encoding = ri.getString(INPUT_ENCODING,ENCODING_DEFAULT);
br = new BufferedReader( new InputStreamReader( instream, encoding));
}
catch( UnsupportedEncodingException uce )
{
String msg = "Unsupported input encoding : " + encoding
+ " for template " + logTag;
throw new ParseErrorException( msg );
}
return evaluate( context, writer, logTag, br );
}
/**
* Renders the input reader using the context into the output writer.
* To be used when a template is dynamically constructed, or want to
* use Velocity as a token replacer.
*
* @param context context to use in rendering input string
* @param writer Writer in which to render the output
* @param logTag string to be used as the template name for log messages
* in case of error
* @param reader Reader containing the VTL to be rendered
*
* @return true if successful, false otherwise. If false, see
* Velocity runtime log
* @throws ParseErrorException The template could not be parsed.
* @throws MethodInvocationException A method on a context object could not be invoked.
* @throws ResourceNotFoundException A referenced resource could not be loaded.
* @throws IOException While reading from the reader or rendering to the writer,
* an I/O problem occured.
* @since Velocity v1.1
*/
public boolean evaluate(Context context, Writer writer,
String logTag, Reader reader)
throws ParseErrorException, MethodInvocationException,
ResourceNotFoundException,IOException
{
return ri.evaluate(context, writer, logTag, reader);
}
/**
* Invokes a currently registered Velocimacro with the params provided
* and places the rendered stream into the writer.
*
* Note : currently only accepts args to the VM if they are in the context.
*
* @param vmName name of Velocimacro to call
* @param logTag string to be used for template name in case of error. if null,
* the vmName will be used
* @param params keys for args used to invoke Velocimacro, in java format
* rather than VTL (eg "foo" or "bar" rather than "$foo" or "$bar")
* @param context Context object containing data/objects used for rendering.
* @param writer Writer for output stream
* @return true if Velocimacro exists and successfully invoked, false otherwise.
* @throws IOException While rendering to the writer, an I/O problem occured.
*/
public boolean invokeVelocimacro( String vmName, String logTag,
String params[], Context context,
Writer writer )
throws Exception
{
return ri.invokeVelocimacro(vmName, logTag, params, context, writer);
}
/**
* Merges a template and puts the rendered stream into the writer.
* The default encoding that Velocity uses to read template files is defined in
* the property input.encoding and defaults to ISO-8859-1.
*
* @param templateName name of template to be used in merge
* @param context filled context to be used in merge
* @param writer writer to write template into
*
* @return true if successful, false otherwise. Errors
* logged to velocity log.
* @throws ResourceNotFoundException
* @throws ParseErrorException
* @throws MethodInvocationException
* @throws Exception
* @deprecated Use
* {@link #mergeTemplate( String templateName, String encoding,
* Context context, Writer writer )}
*/
public boolean mergeTemplate( String templateName,
Context context, Writer writer )
throws ResourceNotFoundException, ParseErrorException, MethodInvocationException, Exception
{
return mergeTemplate( templateName, ri.getString(INPUT_ENCODING,ENCODING_DEFAULT),
context, writer );
}
/**
* merges a template and puts the rendered stream into the writer
*
* @param templateName name of template to be used in merge
* @param encoding encoding used in template
* @param context filled context to be used in merge
* @param writer writer to write template into
*
* @return true if successful, false otherwise. Errors
* logged to velocity log
* @throws ResourceNotFoundException
* @throws ParseErrorException
* @throws MethodInvocationException
* @throws Exception
*
* @since Velocity v1.1
*/
public boolean mergeTemplate( String templateName, String encoding,
Context context, Writer writer )
throws ResourceNotFoundException, ParseErrorException, MethodInvocationException, Exception
{
Template template = ri.getTemplate(templateName, encoding);
if ( template == null )
{
String msg = "VelocityEngine.mergeTemplate() was unable to load template '"
+ templateName + "'";
getLog().error(msg);
throw new ResourceNotFoundException(msg);
}
else
{
template.merge(context, writer);
return true;
}
}
/**
* Returns a Template from the Velocity
* resource management system.
*
* @param name The file name of the desired template.
* @return The 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 Exception if an error occurs in template initialization
*/
public Template getTemplate(String name)
throws ResourceNotFoundException, ParseErrorException, Exception
{
return ri.getTemplate( name );
}
/**
* Returns a Template from the Velocity
* resource management system.
*
* @param name The file name of the desired template.
* @param encoding The character encoding to use for the template.
* @return The 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 Exception if an error occurs in template initialization
*
* @since Velocity v1.1
*/
public Template getTemplate(String name, String encoding)
throws ResourceNotFoundException, ParseErrorException, Exception
{
return ri.getTemplate( name, encoding );
}
/**
* Determines if a resource is accessable via the currently
* configured resource loaders.
*
* Note that the current implementation will not
* change the state of the system in any real way - so this
* cannot be used to pre-load the resource cache, as the
* previous implementation did as a side-effect.
*
* The previous implementation exhibited extreme lazyness and
* sloth, and the author has been flogged.
*
* @param resourceName name of the resource to search for
* @return true if found, false otherwise
* @since 1.5
*/
public boolean resourceExists(String resourceName)
{
return (ri.getLoaderNameForResource(resourceName) != null);
}
/**
* @param resourceName
* @return True if the template exists.
* @see #resourceExists(String)
* @deprecated Use resourceExists(String) instead.
*/
public boolean templateExists(String resourceName)
{
return resourceExists(resourceName);
}
/**
* Returns a convenient Log instance that wraps the current LogChute.
* Use this to log error messages. It has the usual methods you'd expect.
* @return A log object.
* @since 1.5
*/
public Log getLog()
{
return ri.getLog();
}
/**
* @param message
* @deprecated Use getLog() and call warn() on it.
*/
public void warn(Object message)
{
getLog().warn(message);
}
/**
* @param message
* @deprecated Use getLog() and call warn() on it.
*/
public void info(Object message)
{
getLog().info(message);
}
/**
* @param message
* @deprecated Use getLog() and call warn() on it.
*/
public void error(Object message)
{
getLog().error(message);
}
/**
* @param message
* @deprecated Use getLog() and call warn() on it.
*/
public void debug(Object message)
{
getLog().debug(message);
}
/**
*
* Sets an application attribute (which can be any Object) that will be
* accessible from any component of the system that gets a
* RuntimeServices. This allows communication between the application
* environment and custom pluggable components of the Velocity engine,
* such as ResourceLoaders and LogChutes.
*
*
*
* Note that there is no enforcement or rules for the key
* used - it is up to the application developer. However, to
* help make the intermixing of components possible, using
* the target Class name (e.g. com.foo.bar ) as the key
* might help avoid collision.
*
*
* @param key object 'name' under which the object is stored
* @param value object to store under this key
*/
public void setApplicationAttribute( Object key, Object value )
{
ri.setApplicationAttribute(key, value);
}
/**
*
* Return an application attribute (which can be any Object)
* that was set by the application in order to be accessible from
* any component of the system that gets a RuntimeServices.
* This allows communication between the application
* environment and custom pluggable components of the
* Velocity engine, such as ResourceLoaders and LogChutes.
*
*
* @param key object 'name' under which the object is stored
* @return value object to store under this key
* @since 1.5
*/
public Object getApplicationAttribute( Object key )
{
return ri.getApplicationAttribute(key);
}
}
© 2015 - 2024 Weber Informatics LLC | Privacy Policy