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Commons JXPath example source code file (MethodLookupUtils.java)

This example Commons JXPath source code file (MethodLookupUtils.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 - Commons JXPath tags/keywords

ambigous, approximate_match, class, class, constructor, exact_match, jxpathexception, method, method, no_match, no_match, nosuchmethodexception, object, object, reflection, util

The Commons JXPath MethodLookupUtils.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.
 */
package org.apache.commons.jxpath.util;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;

import org.apache.commons.jxpath.ExpressionContext;
import org.apache.commons.jxpath.JXPathException;

/**
 * Method lookup utilities, which find static and non-static methods as well
 * as constructors based on a name and list of parameters.
 *
 * @author Dmitri Plotnikov
 * @version $Revision: 670727 $ $Date: 2008-06-23 15:10:38 -0500 (Mon, 23 Jun 2008) $
 */
public class MethodLookupUtils {

    private static final int NO_MATCH = 0;
    private static final int APPROXIMATE_MATCH = 1;
    private static final int EXACT_MATCH = 2;

    /**
     * Look up a constructor.
     * @param targetClass the class constructed
     * @param parameters arguments
     * @return Constructor found if any.
     */
    public static Constructor lookupConstructor(
        Class targetClass,
        Object[] parameters) {
        boolean tryExact = true;
        int count = parameters == null ? 0 : parameters.length;
        Class[] types = new Class[count];
        for (int i = 0; i < count; i++) {
            Object param = parameters[i];
            if (param != null) {
                types[i] = param.getClass();
            }
            else {
                types[i] = null;
                tryExact = false;
            }
        }

        Constructor constructor = null;

        if (tryExact) {
            // First - without type conversion
            try {
                constructor = targetClass.getConstructor(types);
                if (constructor != null) {
                    return constructor;
                }
            }
            catch (NoSuchMethodException ex) { //NOPMD
                // Ignore
            }
        }

        int currentMatch = 0;
        boolean ambiguous = false;

        // Then - with type conversion
        Constructor[] constructors = targetClass.getConstructors();
        for (int i = 0; i < constructors.length; i++) {
            int match =
                matchParameterTypes(
                    constructors[i].getParameterTypes(),
                    parameters);
            if (match != NO_MATCH) {
                if (match > currentMatch) {
                    constructor = constructors[i];
                    currentMatch = match;
                    ambiguous = false;
                }
                else if (match == currentMatch) {
                    ambiguous = true;
                }
            }
        }
        if (ambiguous) {
            throw new JXPathException(
                "Ambigous constructor " + Arrays.asList(parameters));
        }
        return constructor;
    }

    /**
     * Look up a static method.
     * @param targetClass the owning class
     * @param name method name
     * @param parameters method parameters
     * @return Method found if any
     */
    public static Method lookupStaticMethod(
        Class targetClass,
        String name,
        Object[] parameters) {
        boolean tryExact = true;
        int count = parameters == null ? 0 : parameters.length;
        Class[] types = new Class[count];
        for (int i = 0; i < count; i++) {
            Object param = parameters[i];
            if (param != null) {
                types[i] = param.getClass();
            }
            else {
                types[i] = null;
                tryExact = false;
            }
        }

        Method method = null;

        if (tryExact) {
            // First - without type conversion
            try {
                method = targetClass.getMethod(name, types);
                if (method != null
                    && Modifier.isStatic(method.getModifiers())) {
                    return method;
                }
            }
            catch (NoSuchMethodException ex) { //NOPMD
                // Ignore
            }
        }

        int currentMatch = 0;
        boolean ambiguous = false;

        // Then - with type conversion
        Method[] methods = targetClass.getMethods();
        for (int i = 0; i < methods.length; i++) {
            if (Modifier.isStatic(methods[i].getModifiers())
                && methods[i].getName().equals(name)) {
                int match =
                    matchParameterTypes(
                        methods[i].getParameterTypes(),
                        parameters);
                if (match != NO_MATCH) {
                    if (match > currentMatch) {
                        method = methods[i];
                        currentMatch = match;
                        ambiguous = false;
                    }
                    else if (match == currentMatch) {
                        ambiguous = true;
                    }
                }
            }
        }
        if (ambiguous) {
            throw new JXPathException("Ambigous method call: " + name);
        }
        return method;
    }

    /**
     * Look up a method.
     * @param targetClass owning class
     * @param name method name
     * @param parameters method parameters
     * @return Method found if any
     */
    public static Method lookupMethod(
        Class targetClass,
        String name,
        Object[] parameters) {
        if (parameters == null
            || parameters.length < 1
            || parameters[0] == null) {
            return null;
        }

        if (matchType(targetClass, parameters[0]) == NO_MATCH) {
            return null;
        }

        targetClass = TypeUtils.convert(parameters[0], targetClass).getClass();

        boolean tryExact = true;
        int count = parameters.length - 1;
        Class[] types = new Class[count];
        Object[] arguments = new Object[count];
        for (int i = 0; i < count; i++) {
            Object param = parameters[i + 1];
            arguments[i] = param;
            if (param != null) {
                types[i] = param.getClass();
            }
            else {
                types[i] = null;
                tryExact = false;
            }
        }

        Method method = null;

        if (tryExact) {
            // First - without type conversion
            try {
                method = targetClass.getMethod(name, types);
                if (method != null
                    && !Modifier.isStatic(method.getModifiers())) {
                    return method;
                }
            }
            catch (NoSuchMethodException ex) { //NOPMD
                // Ignore
            }
        }

        int currentMatch = 0;
        boolean ambiguous = false;

        // Then - with type conversion
        Method[] methods = targetClass.getMethods();
        for (int i = 0; i < methods.length; i++) {
            if (!Modifier.isStatic(methods[i].getModifiers())
                && methods[i].getName().equals(name)) {
                int match =
                    matchParameterTypes(
                        methods[i].getParameterTypes(),
                        arguments);
                if (match != NO_MATCH) {
                    if (match > currentMatch) {
                        method = methods[i];
                        currentMatch = match;
                        ambiguous = false;
                    }
                    else if (match == currentMatch) {
                        ambiguous = true;
                    }
                }
            }
        }
        if (ambiguous) {
            throw new JXPathException("Ambigous method call: " + name);
        }
        return method;
    }

    /**
     * Return a match code of objects to types.
     * @param types Class[] of expected types
     * @param parameters Object[] to attempt to match
     * @return int code
     */
    private static int matchParameterTypes(
        Class[] types,
        Object[] parameters) {
        int pi = 0;
        if (types.length >= 1
            && ExpressionContext.class.isAssignableFrom(types[0])) {
            pi++;
        }
        int length = parameters == null ? 0 : parameters.length;
        if (types.length != length + pi) {
            return NO_MATCH;
        }
        int totalMatch = EXACT_MATCH;
        for (int i = 0; i < length; i++) {
            int match = matchType(types[i + pi], parameters[i]);
            if (match == NO_MATCH) {
                return NO_MATCH;
            }
            if (match < totalMatch) {
                totalMatch = match;
            }
        }
        return totalMatch;
    }

    /**
     * Return a match code between an object and type.
     * @param expected class to test
     * @param object object to test
     * @return int code
     */
    private static int matchType(Class expected, Object object) {
        if (object == null) {
            return APPROXIMATE_MATCH;
        }

        Class actual = object.getClass();

        if (expected.equals(actual)) {
            return EXACT_MATCH;
        }
        if (expected.isAssignableFrom(actual)) {
            return EXACT_MATCH;
        }

        if (TypeUtils.canConvert(object, expected)) {
            return APPROXIMATE_MATCH;
        }

        return NO_MATCH;
    }
}

Other Commons JXPath examples (source code examples)

Here is a short list of links related to this Commons JXPath MethodLookupUtils.java source code file:

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