astreference.java

velocity 的脚本语言的全部代码集合

package org.apache.velocity.runtime.parser.node;

/*
 * Copyright 2000-2002,2004 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.Writer;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;

import org.apache.velocity.context.Context;
import org.apache.velocity.context.InternalContextAdapter;
import org.apache.velocity.runtime.RuntimeConstants;
import org.apache.velocity.runtime.exception.ReferenceException;
import org.apache.velocity.runtime.parser.*;

import org.apache.velocity.util.introspection.VelPropertySet;
import org.apache.velocity.util.introspection.Info;

import org.apache.velocity.exception.MethodInvocationException;

import org.apache.velocity.app.event.EventCartridge;

/**
 * This class is responsible for handling the references in
 * VTL ($foo).
 *
 * Please look at the Parser.jjt file which is
 * what controls the generation of this class.
 *
 * @author <a href="mailto:[e-mail]">Jason van Zyl</a>
 * @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]>Kent Johnson</a>
 * @version $Id: ASTReference.java,v 1.49.4.1 2004/03/03 23:22:59 geirm Exp $
*/
public class ASTReference extends SimpleNode
{
    /* Reference types */
    private static final int NORMAL_REFERENCE = 1;
    private static final int FORMAL_REFERENCE = 2;
    private static final int QUIET_REFERENCE = 3;
    private static final int RUNT = 4;

    private int referenceType;
    private String nullString;
    private String rootString;
    private boolean escaped = false;
    private boolean computableReference = true;
    private String escPrefix = "";
    private String morePrefix = "";
    private String identifier = "";

    private String literal = null;

    private int numChildren = 0;

    protected Info uberInfo;

    public ASTReference(int id)
    {
        super(id);
    }

    public ASTReference(Parser p, int id)
    {
        super(p, id);
    }

    /** Accept the visitor. **/
    public Object jjtAccept(ParserVisitor visitor, Object data)
    {
        return visitor.visit(this, data);
    }

    public Object init(InternalContextAdapter context, Object data)
        throws Exception
    {
        /*
         *  init our children
         */

        super.init(context, data);

        /*
         *  the only thing we can do in init() is getRoot()
         *  as that is template based, not context based,
         *  so it's thread- and context-safe
         */

        rootString = getRoot();

        numChildren = jjtGetNumChildren();

        /*
         * and if appropriate...
         */

        if (numChildren > 0 )
        {
            identifier = jjtGetChild(numChildren - 1).getFirstToken().image;
        }

        /*
         * make an uberinfo - saves new's later on
         */

        uberInfo = new Info(context.getCurrentTemplateName(),
                getLine(),getColumn());

        return data;
    }

    /**
     *  Returns the 'root string', the reference key
     */
     public String getRootString()
     {
        return rootString;
     }

    /**
     *   gets an Object that 'is' the value of the reference
     *
     *   @param o   unused Object parameter
     *   @param context context used to generate value
     */
    public Object execute(Object o, InternalContextAdapter context)
        throws MethodInvocationException
    {

        if (referenceType == RUNT)
            return null;

        /*
         *  get the root object from the context
         */

        Object result = getVariableValue(context, rootString);

        if (result == null)
        {
            return null;
        }

        /*
         * Iteratively work 'down' (it's flat...) the reference
         * to get the value, but check to make sure that
         * every result along the path is valid. For example:
         *
         * $hashtable.Customer.Name
         *
         * The $hashtable may be valid, but there is no key
         * 'Customer' in the hashtable so we want to stop
         * when we find a null value and return the null
         * so the error gets logged.
         */

        try
        {
            for (int i = 0; i < numChildren; i++)
            {
                result = jjtGetChild(i).execute(result,context);

                if (result == null)
                {
                    return null;
                }
            }

            return result;
        }
        catch(MethodInvocationException mie)
        {
            /*
             *  someone tossed their cookies
             */

            rsvc.error("Method " + mie.getMethodName()
                        + " threw exception for reference $"
                        + rootString
                        + " in template " + context.getCurrentTemplateName()
                        + " at " +  " [" + this.getLine() + ","
                        + this.getColumn() + "]");

            mie.setReferenceName(rootString);
            throw mie;
        }
    }

    /**
     *  gets the value of the reference and outputs it to the
     *  writer.
     *
     *  @param context  context of data to use in getting value
     *  @param writer   writer to render to
     */
    public boolean render(InternalContextAdapter context, Writer writer)
        throws IOException, MethodInvocationException
    {

        if (referenceType == RUNT)
        {
            writer.write(rootString);
            return true;
        }

        Object value = execute(null, context);

        /*
         *  if this reference is escaped (\$foo) then we want to do one of two things :
         *  1) if this is a reference in the context, then we want to print $foo
         *  2) if not, then \$foo  (its considered shmoo, not VTL)
         */

        if (escaped)
        {
            if (value == null)
            {
                writer.write(escPrefix);
                writer.write("\\");
                writer.write(nullString);
            }
            else
            {
                writer.write(escPrefix);
                writer.write(nullString);
            }

            return true;
        }

        /*
         *  the normal processing
         *
         *  if we have an event cartridge, get a new value object
         */

        EventCartridge ec = context.getEventCartridge();

        if (ec != null)
        {
            value =  ec.referenceInsert(literal(), value);
        }

        /*
         *  if value is null...
         */

        if (value == null)
        {
            /*
             *  write prefix twice, because it's shmoo, so the \ don't escape each other...
             */

            writer.write(escPrefix);
            writer.write(escPrefix);
            writer.write(morePrefix);
            writer.write(nullString);

            if (referenceType != QUIET_REFERENCE
                && rsvc.getBoolean(RuntimeConstants.RUNTIME_LOG_REFERENCE_LOG_INVALID,
                        true))
            {
               rsvc.warn(new ReferenceException("reference : template = "
                                + context.getCurrentTemplateName(), this));
            }

            return true;
        }
        else
        {
            /*
             *  non-null processing
             */

            writer.write(escPrefix);
            writer.write(morePrefix);
            writer.write(value.toString());

            return true;
        }
    }

    /**
     *   Computes boolean value of this reference
     *   Returns the actual value of reference return type
     *   boolean, and 'true' if value is not null
     *
     *   @param context context to compute value with
     */
    public boolean evaluate(InternalContextAdapter context)
        throws MethodInvocationException
    {
        Object value = execute(null, context);

        if (value == null)
        {
            return false;
        }
        else if (value instanceof Boolean)
        {
            if (((Boolean) value).booleanValue())
                return true;
            else
                return false;
        }
        else
            return true;
    }

    public Object value(InternalContextAdapter context)
        throws MethodInvocationException
    {
        return (computableReference ? execute(null, context) : null);
    }

    /**
     *  Sets the value of a complex reference (something like $foo.bar)
     *  Currently used by ASTSetReference()