Java Reflection Method Signature getMethodByFunctionSignature(Class clazz, String signature)

Description

Finds method by function signature string which is compliant with Tag Library function signature in Java Server Page (TM) Specification.

License

Apache License

Parameter

Parameter	Description
clazz	Class having the method.
signature	Java Server Page (TM) Specification compliant function signature string.

Return

method if found.

Declaration

public static Method getMethodByFunctionSignature(Class clazz,
        String signature) throws SecurityException,
        NoSuchMethodException, ClassNotFoundException

Method Source Code

//package com.java2s;
/*/*from w w w.j  a  v  a2  s . co  m*/
 * 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.
 */

import java.lang.reflect.Method;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import freemarker.template.utility.ClassUtil;
import freemarker.template.utility.StringUtil;

public class Main {
    private static final Pattern FUNCTION_SIGNATURE_PATTERN = Pattern
            .compile("^([\\w\\.]+(\\s*\\[\\s*\\])?)\\s+([\\w]+)\\s*\\((.*)\\)$");
    private static final Pattern FUNCTION_PARAMETER_PATTERN = Pattern
            .compile("^([\\w\\.]+)(\\s*\\[\\s*\\])?$");

    /**
     * Finds method by function signature string which is compliant with
     * Tag Library function signature in Java Server Page (TM) Specification.
     * A function signature example is as follows: {@code java.lang.String nickName( java.lang.String, int)}
     * 
     * @param clazz Class having the method.
     * @param signature Java Server Page (TM) Specification compliant function signature string.
     * @return method if found.
     */
    public static Method getMethodByFunctionSignature(Class clazz,
            String signature) throws SecurityException,
            NoSuchMethodException, ClassNotFoundException {
        Matcher m1 = FUNCTION_SIGNATURE_PATTERN.matcher(signature);

        if (!m1.matches()) {
            throw new IllegalArgumentException(
                    "Invalid function signature.");
        }

        String methodName = m1.group(3);
        String params = m1.group(4).trim();
        Class[] paramTypes = null;

        if ("".equals(params)) {
            paramTypes = new Class[0];
        } else {
            String[] paramsArray = StringUtil.split(params, ',');
            paramTypes = new Class[paramsArray.length];
            String token = null;
            String paramType = null;
            boolean isPrimitive = false;
            boolean isArrayType = false;
            Matcher m2 = null;

            for (int i = 0; i < paramsArray.length; i++) {
                token = paramsArray[i].trim();
                m2 = FUNCTION_PARAMETER_PATTERN.matcher(token);

                if (!m2.matches()) {
                    throw new IllegalArgumentException(
                            "Invalid argument signature: '" + token + "'.");
                }

                paramType = m2.group(1);
                isPrimitive = (paramType.indexOf('.') == -1);
                isArrayType = (m2.group(2) != null);

                if (isPrimitive) {
                    if ("byte".equals(paramType)) {
                        paramTypes[i] = (isArrayType ? byte[].class
                                : byte.class);
                    } else if ("short".equals(paramType)) {
                        paramTypes[i] = (isArrayType ? short[].class
                                : short.class);
                    } else if ("int".equals(paramType)) {
                        paramTypes[i] = (isArrayType ? int[].class
                                : int.class);
                    } else if ("long".equals(paramType)) {
                        paramTypes[i] = (isArrayType ? long[].class
                                : long.class);
                    } else if ("float".equals(paramType)) {
                        paramTypes[i] = (isArrayType ? float[].class
                                : float.class);
                    } else if ("double".equals(paramType)) {
                        paramTypes[i] = (isArrayType ? double[].class
                                : double.class);
                    } else if ("boolean".equals(paramType)) {
                        paramTypes[i] = (isArrayType ? boolean[].class
                                : boolean.class);
                    } else if ("char".equals(paramType)) {
                        paramTypes[i] = (isArrayType ? char[].class
                                : char.class);
                    } else {
                        throw new IllegalArgumentException(
                                "Invalid primitive type: '" + paramType
                                        + "'.");
                    }
                } else {
                    if (isArrayType) {
                        paramTypes[i] = ClassUtil.forName("[L" + paramType
                                + ";");
                    } else {
                        paramTypes[i] = ClassUtil.forName(paramType);
                    }
                }
            }
        }

        return clazz.getMethod(methodName, paramTypes);
    }
}

Java Reflection Method Signature getMethodByFunctionSignature(Class clazz, String signature)

Description

License

Parameter

Return

Declaration

Method Source Code

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