Struts example source code file (AstValue.java)

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

Java - Struts tags/keywords

astvalue, class, class, coerce_to_zero, elexception, elexception, elresolver, illegalaccessexception, method, object, object, reflection, simplenode, target, target

The Struts AstValue.java source code

/*
 * 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.
 */
/* Generated By:JJTree: Do not edit this line. AstValue.java */

package org.apache.struts2.el.parser;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.MethodInfo;
import javax.el.PropertyNotFoundException;

import org.apache.struts2.el.lang.ELSupport;
import org.apache.struts2.el.lang.EvaluationContext;
import org.apache.struts2.el.util.MessageFactory;
import org.apache.struts2.el.util.ReflectionUtil;


/**
 * @author Jacob Hookom [jacob@hookom.net]
 * @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: markt $
 */
public final class AstValue extends SimpleNode {

    protected static final boolean COERCE_TO_ZERO =
        Boolean.valueOf(System.getProperty(
                "org.apache.el.parser.COERCE_TO_ZERO", "true")).booleanValue();
    
    protected static class Target {
        protected Object base;

        protected Object property;
    }

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

    public Class getType(EvaluationContext ctx) throws ELException {
        Target t = getTarget(ctx);
        ctx.setPropertyResolved(false);
        return ctx.getELResolver().getType(ctx, t.base, t.property);
    }

    private final Target getTarget(EvaluationContext ctx) throws ELException {
        // evaluate expr-a to value-a
        Object base = this.children[0].getValue(ctx);

        // if our base is null (we know there are more properites to evaluate)
        if (base == null) {
            throw new PropertyNotFoundException(MessageFactory.get(
                    "error.unreachable.base", this.children[0].getImage()));
        }

        // set up our start/end
        Object property = null;
        int propCount = this.jjtGetNumChildren() - 1;
        int i = 1;

        // evaluate any properties before our target
        ELResolver resolver = ctx.getELResolver();
        if (propCount > 1) {
            while (base != null && i < propCount) {
                property = this.children[i].getValue(ctx);
                ctx.setPropertyResolved(false);
                base = resolver.getValue(ctx, base, property);
                i++;
            }
            // if we are in this block, we have more properties to resolve,
            // but our base was null
            if (base == null || property == null) {
                throw new PropertyNotFoundException(MessageFactory.get(
                        "error.unreachable.property", property));
            }
        }

        property = this.children[i].getValue(ctx);

        if (property == null) {
            throw new PropertyNotFoundException(MessageFactory.get(
                    "error.unreachable.property", this.children[i]));
        }

        Target t = new Target();
        t.base = base;
        t.property = property;
        return t;
    }

    public Object getValue(EvaluationContext ctx) throws ELException {
        Object base = this.children[0].getValue(ctx);
        int propCount = this.jjtGetNumChildren();
        int i = 1;
        Object property = null;
        ELResolver resolver = ctx.getELResolver();
        while (base != null && i < propCount) {
            property = this.children[i].getValue(ctx);
            if (property == null) {
                return null;
            } else {
                ctx.setPropertyResolved(false);
                base = resolver.getValue(ctx, base, property);
            }
            i++;
        }
        return base;
    }

    public boolean isReadOnly(EvaluationContext ctx) throws ELException {
        Target t = getTarget(ctx);
        ctx.setPropertyResolved(false);
        return ctx.getELResolver().isReadOnly(ctx, t.base, t.property);
    }

    public void setValue(EvaluationContext ctx, Object value)
            throws ELException {
        Target t = getTarget(ctx);
        ctx.setPropertyResolved(false);
        ELResolver resolver = ctx.getELResolver();

        // coerce to the expected type
        Class<?> targetClass = resolver.getType(ctx, t.base, t.property);
        if (COERCE_TO_ZERO == true
                || !isAssignable(value, targetClass)) {
            value = ELSupport.coerceToType(value, targetClass);
        }
        resolver.setValue(ctx, t.base, t.property, value);
    }

    private boolean isAssignable(Object value, Class<?> targetClass) {
        if (targetClass == null) {
            return false;
        } else if (value != null && targetClass.isPrimitive()) {
            return false;
        } else if (value != null && !targetClass.isInstance(value)) {
            return false;
        }
        return true;
    }


    public MethodInfo getMethodInfo(EvaluationContext ctx, Class[] paramTypes)
            throws ELException {
        Target t = getTarget(ctx);
        Method m = ReflectionUtil.getMethod(t.base, t.property, paramTypes);
        return new MethodInfo(m.getName(), m.getReturnType(), m
                .getParameterTypes());
    }

    public Object invoke(EvaluationContext ctx, Class[] paramTypes,
            Object[] paramValues) throws ELException {
        Target t = getTarget(ctx);
        Method m = ReflectionUtil.getMethod(t.base, t.property, paramTypes);
        Object result = null;
        try {
            result = m.invoke(t.base, (Object[]) paramValues);
        } catch (IllegalAccessException iae) {
            throw new ELException(iae);
        } catch (InvocationTargetException ite) {
            throw new ELException(ite.getCause());
        }
        return result;
    }
}