velocity.java

velocity官方工具包 包括各种JAR包 示例 文档等

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.StringReader;
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.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.runtime.RuntimeConstants;
import org.apache.velocity.runtime.RuntimeSingleton;
import org.apache.velocity.runtime.log.Log;
import org.apache.velocity.runtime.parser.ParseException;
import org.apache.velocity.runtime.parser.node.SimpleNode;

/**
 * This class provides  services to the application
 * developer, such as :
 * <ul>
 * <li> Simple Velocity Runtime engine initialization methods.
 * <li> Functions to apply the template engine to streams and strings
 *      to allow embedding and dynamic template generation.
 * <li> Methods to access Velocimacros directly.
 * </ul>
 *
 * <br><br>
 * While the most common way to use Velocity is via templates, as
 * Velocity is a general-purpose template engine, there are other
 * uses that Velocity is well suited for, such as processing dynamically
 * created templates, or processing content streams.
 *
 * <br><br>
 * The methods herein were developed to allow easy access to the Velocity
 * facilities without direct spelunking of the internals.  If there is
 * something you feel is necessary to add here, please, send a patch.
 *
 * @author <a href="mailto:[e-mail]">Geir Magnusson Jr.</a>
 * @author <a href="mailto:[e-mail]">Christoph Reck</a>
 * @author <a href="mailto:[e-mail]">Jason van Zyl</a>
 * @version $Id: Velocity.java 471381 2006-11-05 08:56:58Z wglass $
 */
public class Velocity implements RuntimeConstants
{
    /**
     *  initialize the Velocity runtime engine, using the default
     *  properties of the Velocity distribution
     *
     * @throws Exception When an error during initialization occurs.
     */
    public static void init()
        throws Exception
    {
        RuntimeSingleton.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 When an error during initialization occurs.
     */
    public static void init( String propsFilename )
        throws Exception
    {
        RuntimeSingleton.init(propsFilename);
    }

    /**
     *  initialize the Velocity runtime engine, using default properties
     *  plus the properties in the passed in java.util.Properties object
     *
     *  @param p  Properties object containing initialization properties
     * @throws Exception When an error during initialization occurs.
     *
     */
    public static void init( Properties p )
        throws Exception
    {
        RuntimeSingleton.init( p );
    }

    /**
     * Set a Velocity Runtime property.
     *
     * @param key The property key.
     * @param value The property value.
     */
    public static void setProperty(String key, Object value)
    {
        RuntimeSingleton.setProperty(key,value);
    }

    /**
     * Add a Velocity Runtime property.
     *
     * @param key The property key.
     * @param value The property value.
     */
    public static void addProperty(String key, Object value)
    {
        RuntimeSingleton.addProperty(key,value);
    }

    /**
     * Clear a Velocity Runtime property.
     *
     * @param key of property to clear
     */
    public static void clearProperty(String key)
    {
        RuntimeSingleton.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 A configuration object.
     *
     */
    public static void setExtendedProperties( ExtendedProperties configuration)
    {
        RuntimeSingleton.setConfiguration( configuration );
    }

    /**
     *  Get a Velocity Runtime property.
     *
     *  @param key property to retrieve
     *  @return property value or null if the property
     *        not currently set
     */
    public static Object getProperty( String key )
    {
        return RuntimeSingleton.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 loading a reference, an I/O problem occured.
     */
    public static  boolean evaluate( Context context,  Writer out,
                                     String logTag, String instring )
        throws ParseErrorException, MethodInvocationException,
            ResourceNotFoundException, IOException
    {
        return evaluate( context, out, logTag, new BufferedReader( new StringReader( 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
     *  @deprecated Use
     *  {@link #evaluate( Context context, Writer writer,
     *      String logTag, Reader reader ) }
     * @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 loading a reference, an I/O problem occured.
     */
    public static 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 = RuntimeSingleton.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 loading a reference, an I/O problem occured.
     *
     *  @since Velocity v1.1
     */
    public static boolean evaluate( Context context, Writer writer,
                                    String logTag, Reader reader )
        throws ParseErrorException, MethodInvocationException,
            ResourceNotFoundException,IOException
    {
        SimpleNode nodeTree = null;

        try
        {
            nodeTree = RuntimeSingleton.parse( reader, logTag );
        }
        catch ( ParseException pex )
        {
            throw  new ParseErrorException( pex );
        }
        catch (TemplateInitException pex)
        {
            throw  new ParseErrorException( pex );
        }

        /*
         * now we want to init and render
         */

        if (nodeTree != null)
        {
            InternalContextAdapterImpl ica =
                new InternalContextAdapterImpl( context );

            ica.pushCurrentTemplateName( logTag );

            try
            {
                try
                {
                    nodeTree.init( ica, RuntimeSingleton.getRuntimeServices() );
                }
                catch (TemplateInitException pex)
                {
                    throw  new ParseErrorException( pex );
                }
                /**
                 * pass through application level runtime exceptions
                 */
                catch( RuntimeException e )
                {
                    throw e;
                }
                catch( Exception e )
                {
                    getLog().error("Velocity.evaluate() : init exception for tag = "+logTag, e);
                }