alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (FunctionAvailableCall.java)

This example Java source code file (FunctionAvailableCall.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

class, classnotfoundexception, constantpoolgen, errormsg, expression, functionavailablecall, functioncall, literalexpr, object, parser, push, reflection, string, typecheckerror, util, vector

The FunctionAvailableCall.java Java example source code

/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
/*
 * Copyright 2001-2004 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.
 */
/*
 * $Id: FunctionAvailableCall.java,v 1.2.4.1 2005/09/01 15:30:25 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Vector;

import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.PUSH;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ErrorMsg;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Util;
import com.sun.org.apache.xalan.internal.utils.ObjectFactory;

/**
 * @author G. Todd Miller
 * @author Santiago Pericas-Geertsen
 */
final class FunctionAvailableCall extends FunctionCall {

    private Expression _arg;
    private String     _nameOfFunct = null;
    private String     _namespaceOfFunct = null;
    private boolean    _isFunctionAvailable = false;

    /**
     * Constructs a FunctionAvailableCall FunctionCall. Takes the
     * function name qname, for example, 'function-available', and
     * a list of arguments where the arguments must be instances of
     * LiteralExpression.
     */
    public FunctionAvailableCall(QName fname, Vector arguments) {
        super(fname, arguments);
        _arg = (Expression)arguments.elementAt(0);
        _type = null;

        if (_arg instanceof LiteralExpr) {
            LiteralExpr arg = (LiteralExpr) _arg;
            _namespaceOfFunct = arg.getNamespace();
            _nameOfFunct = arg.getValue();

            if (!isInternalNamespace()) {
              _isFunctionAvailable = hasMethods();
            }
        }
    }

    /**
     * Argument of function-available call must be literal, typecheck
     * returns the type of function-available to be boolean.
     */
    public Type typeCheck(SymbolTable stable) throws TypeCheckError {
        if (_type != null) {
           return _type;
        }
        if (_arg instanceof LiteralExpr) {
            return _type = Type.Boolean;
        }
        ErrorMsg err = new ErrorMsg(ErrorMsg.NEED_LITERAL_ERR,
                        "function-available", this);
        throw new TypeCheckError(err);
    }

    /**
     * Returns an object representing the compile-time evaluation
     * of an expression. We are only using this for function-available
     * and element-available at this time.
     */
    public Object evaluateAtCompileTime() {
        return getResult() ? Boolean.TRUE : Boolean.FALSE;
    }

    /**
     * for external java functions only: reports on whether or not
     * the specified method is found in the specifed class.
     */
    private boolean hasMethods() {
        LiteralExpr arg = (LiteralExpr)_arg;

        // Get the class name from the namespace uri
        String className = getClassNameFromUri(_namespaceOfFunct);

        // Get the method name from the argument to function-available
        String methodName = null;
        int colonIndex = _nameOfFunct.indexOf(":");
        if (colonIndex > 0) {
          String functionName = _nameOfFunct.substring(colonIndex+1);
          int lastDotIndex = functionName.lastIndexOf('.');
          if (lastDotIndex > 0) {
            methodName = functionName.substring(lastDotIndex+1);
            if (className != null && !className.equals(""))
              className = className + "." + functionName.substring(0, lastDotIndex);
            else
              className = functionName.substring(0, lastDotIndex);
          }
          else
            methodName = functionName;
        }
        else
          methodName = _nameOfFunct;

        if (className == null || methodName == null) {
            return false;
        }

        // Replace the '-' characters in the method name
        if (methodName.indexOf('-') > 0)
          methodName = replaceDash(methodName);

        try {
            final Class clazz = ObjectFactory.findProviderClass(className, true);

            if (clazz == null) {
                return false;
            }

            final Method[] methods = clazz.getMethods();

            for (int i = 0; i < methods.length; i++) {
                final int mods = methods[i].getModifiers();

                if (Modifier.isPublic(mods) && Modifier.isStatic(mods)
                        && methods[i].getName().equals(methodName))
                {
                    return true;
                }
            }
        }
        catch (ClassNotFoundException e) {
          return false;
        }
        return false;
    }

    /**
     * Reports on whether the function specified in the argument to
     * xslt function 'function-available' was found.
     */
    public boolean getResult() {
        if (_nameOfFunct == null) {
            return false;
        }

        if (isInternalNamespace()) {
            final Parser parser = getParser();
            _isFunctionAvailable =
                parser.functionSupported(Util.getLocalName(_nameOfFunct));
        }
        return _isFunctionAvailable;
    }

    /**
     * Return true if the namespace uri is null or it is the XSLTC translet uri.
     */
    private boolean isInternalNamespace() {
        return (_namespaceOfFunct == null ||
            _namespaceOfFunct.equals(EMPTYSTRING) ||
            _namespaceOfFunct.equals(TRANSLET_URI));
    }

    /**
     * Calls to 'function-available' are resolved at compile time since
     * the namespaces declared in the stylsheet are not available at run
     * time. Consequently, arguments to this function must be literals.
     */
    public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
        final ConstantPoolGen cpg = classGen.getConstantPool();
        methodGen.getInstructionList().append(new PUSH(cpg, getResult()));
    }

}

Other Java examples (source code examples)

Here is a short list of links related to this Java FunctionAvailableCall.java source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.