org.apache.hadoop.hbase.util.ParamFormatHelper.java Source code

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Here is the source code for org.apache.hadoop.hbase.util.ParamFormatHelper.java

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/**
 * Copyright 2011 The Apache Software Foundation
 *
 * 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.hadoop.hbase.util;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/**
 * Helper class that uses reflection to iterate through a class and find
 * "pretty print" annotations of methods.  It constructs the pretty print
 * classes, and allows you to easily call getMap given the method and params
 */
public class ParamFormatHelper<TContext> {
    Map<Method, ParamFormatter<TContext>> paramFormatters = new HashMap<Method, ParamFormatter<TContext>>();

    public static final Log LOG = LogFactory.getLog(ParamFormatHelper.class);

    TContext context;

    /**
     * General constructor which allows you to specify the context, clazz and
     * formatType individually
     * @param context the context to use when calling ParamFormatter instances
     * @param clazz the Class to reflect over to get the ParamFormat annotations
     * @param formatType which formatTypes to use (ignores others)
     */
    public ParamFormatHelper(TContext context, Class<?> clazz, ParamFormat.FormatTypes formatType) {
        this.context = context;

        for (Method method : clazz.getMethods()) {
            for (Annotation ann : method.getAnnotations()) {

                if (!(ann instanceof ParamFormat))
                    continue;
                ParamFormat paramFormat = (ParamFormat) ann;
                if (paramFormat.formatType() != formatType)
                    continue;

                try {
                    // getMethod throws if it wasn't derived from ParamFormatter<TContext>
                    paramFormat.clazz().getMethod("getMap", Object[].class, clazz);

                    // The generic constraint in the annotation checks this...
                    @SuppressWarnings("unchecked")
                    ParamFormatter<TContext> newFormatter = (ParamFormatter<TContext>) paramFormat.clazz()
                            .newInstance();

                    paramFormatters.put(method, newFormatter);
                } catch (InstantiationException e) {
                    String msg = "Can not create " + ((ParamFormat) ann).clazz().getName()
                            + " make sure it's public (and static if nested)";
                    throw new RuntimeException(msg, e);
                } catch (NoSuchMethodException e) {
                    // This exception is thrown if the class clazz was derived
                    //  from a different TContext
                } catch (IllegalAccessException e) {
                    String msg = "Can not create " + ((ParamFormat) ann).clazz().getName()
                            + " make sure it's public (and static if nested)";
                    throw new RuntimeException(msg, e);
                }
            }
        }

    }

    /**
     * Default constructor that uses context as the context and class, and
     * DEFAULT formatType
     * @param context the context to use for calling ParamFormatter instances
     *                and for getting the ParamFormat annotations from
     */
    public ParamFormatHelper(TContext context) {
        this(context, context.getClass(), ParamFormat.FormatTypes.DEFAULT);
    }

    /**
     * Try to get info about a method given it's params
     * @param method which method was called
     * @param params the params which the method was called with
     * @return map of information about the call
     */
    public Map<String, Object> getMap(Method method, Object[] params) {
        ParamFormatter<TContext> formatter = paramFormatters.get(method);
        if (formatter == null)
            return null;
        return formatter.getMap(params, context);
    }
}