velocityengine.java

velocity 的脚本语言的全部代码集合

        if (nodeTree != null)
        {
            InternalContextAdapterImpl ica = 
                new InternalContextAdapterImpl( context );
            
            ica.pushCurrentTemplateName( logTag );
            
            try
            {
                try
                {
                    nodeTree.init( ica, ri );
                }
                catch( Exception e )
                {
                    ri.error("Velocity.evaluate() : init exception for tag = " 
                                  + logTag + " : " + e );
                }
                
                /*
                 *  now render, and let any exceptions fly
                 */

                nodeTree.render( ica, writer );
            }
            finally
            {
                ica.popCurrentTemplateName();
            }
            
            return true;
        }
        
        return false;
    }

   
    /**
     *  Invokes a currently registered Velocimacro with the parms 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
     *  @param params[] args used to invoke Velocimacro. In context key format : 
     *                  eg  "foo","bar" (rather than "$foo","$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.
     */
    public boolean invokeVelocimacro( String vmName, String logTag, 
                                              String params[], Context context, 
                                              Writer writer )
        throws Exception
    {
        /*
         *  check parms
         */

        if ( vmName == null ||  params == null ||  context == null 
             || writer == null || logTag == null)
        {
            ri.error( "VelocityEngine.invokeVelocimacro() : invalid parameter");
            return false;
        }

        /*
         * does the VM exist?
         */
          
        if (!ri.isVelocimacro( vmName, logTag ))
        {
            ri.error( "VelocityEngine.invokeVelocimacro() : VM '"+ vmName 
                           + "' not registered.");
            return false;
        }

        /*
         *  now just create the VM call, and use evaluate
         */

        StringBuffer construct = new StringBuffer("#");

        construct.append( vmName );
        construct.append( "(" );
 
        for( int i = 0; i < params.length; i++)
        {
            construct.append( " $" );
            construct.append( params[i] );
        }

        construct.append(" )");

        try
        {
            boolean retval = evaluate(  context,  writer,  
                                         logTag, construct.toString() );
  
            return retval;
        }
        catch( Exception  e )
        {
            ri.error( "VelocityEngine.invokeVelocimacro() : error " + e );
            throw e;
        }
    }

    /**
     *  merges a template and puts the rendered stream into the writer
     *
     *  @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.
     * *  @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
     *
     *  @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 )
        {
            ri.error("Velocity.parseTemplate() failed loading template '" 
                          + templateName + "'" );
            return false;
        }
        else
        {
            template.merge(context, writer);
            return true;
         }
    }

    /**
     *  Returns a <code>Template</code> 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 <code>Template</code> 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 template is accessable via the currently 
     *   configured resource loaders.
     *   <br><br>
     *   Note that the current implementation will <b>not</b>
     *   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. 
     *   <br><br>
     *   The previous implementation exhibited extreme lazyness and
     *   sloth, and the author has been flogged.
     *
     *   @param templateName  name of the temlpate to search for
     *   @return true if found, false otherwise
     */
    public boolean templateExists( String templateName )
    {
        return (ri.getLoaderNameForResource(templateName) != null);
    }
    
    /**
     * Log a warning message.
     *
     * @param Object message to log
     */
    public void warn(Object message)
    {
        ri.warn( message );
    }
    
    /** 
     * Log an info message.
     *
     * @param Object message to log
     */
    public void info(Object message)
    {
        ri.info( message );
    }
    
    /**
     * Log an error message.
     *
     * @param Object message to log
     */
    public void error(Object message)
    {
        ri.error( message );
    }
    
    /**
     * Log a debug message.
     *
     * @param Object message to log
     */
    public void debug(Object message)
    {
        ri.debug( message );
    }

    /**
     *  <p>
     *  Set the an ApplicationAttribue, which is an Object
     *  set by the application which is accessable 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 loaders and loggers.
     *  </p>
     *
     *  <p>
     *  Note that there is no enfocement 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.
     *  </p>
     *
     *  @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 );
     }
}