PropertyGetter xref

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    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements.  See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache License, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License.  You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   */
    17
    18  package org.apache.log4j.config;
    19
    20  import org.apache.log4j.Priority;
    21  import org.apache.log4j.helpers.LogLog;
    22
    23  import java.beans.BeanInfo;
    24  import java.beans.IntrospectionException;
    25  import java.beans.Introspector;
    26  import java.beans.PropertyDescriptor;
    27  import java.io.InterruptedIOException;
    28  import java.lang.reflect.InvocationTargetException;
    29  import java.lang.reflect.Method;
    30
    31
    32  /**
    33     Used for inferring configuration information for a log4j's component.
    34
    35     @author  Anders Kristensen
    36   */
    37  public class PropertyGetter {
    38    protected static final Object[] NULL_ARG = new Object[] {};
    39    protected Object obj;
    40    protected PropertyDescriptor[] props;
    41
    42    public interface PropertyCallback {
    43      void foundProperty(Object obj, String prefix, String name, Object value);
    44    }
    45
    46    /**
    47      Create a new PropertyGetter for the specified Object. This is done
    48      in prepartion for invoking {@link
    49      #getProperties(PropertyGetter.PropertyCallback, String)} one or
    50      more times.
    51
    52      @param obj the object for which to set properties */
    53    public
    54    PropertyGetter(Object obj) throws IntrospectionException {
    55      BeanInfo bi = Introspector.getBeanInfo(obj.getClass());
    56      props = bi.getPropertyDescriptors();
    57      this.obj = obj;
    58    }
    59
    60    public
    61    static
    62    void getProperties(Object obj, PropertyCallback callback, String prefix) {
    63      try {
    64        new PropertyGetter(obj).getProperties(callback, prefix);
    65      } catch (IntrospectionException ex) {
    66        LogLog.error("Failed to introspect object " + obj, ex);
    67      }
    68    }
    69
    70    public
    71    void getProperties(PropertyCallback callback, String prefix) {
    72      for (int i = 0; i < props.length; i++) {
    73        Method getter = props[i].getReadMethod();
    74        if (getter == null) continue;
    75        if (!isHandledType(getter.getReturnType())) {
    76  	//System.err.println("Ignoring " + props[i].getName() +" " + getter.getReturnType());
    77  	continue;
    78        }
    79        String name = props[i].getName();
    80        try {
    81  	Object result = getter.invoke(obj, NULL_ARG);
    82  	//System.err.println("PROP " + name +": " + result);
    83  	if (result != null) {
    84  	  callback.foundProperty(obj, prefix, name, result);
    85  	}
    86        } catch (IllegalAccessException ex) {
    87  	    LogLog.warn("Failed to get value of property " + name);
    88        } catch (InvocationTargetException ex) {
    89          if (ex.getTargetException() instanceof InterruptedException
    90                  || ex.getTargetException() instanceof InterruptedIOException) {
    91              Thread.currentThread().interrupt();
    92          }
    93          LogLog.warn("Failed to get value of property " + name);
    94        } catch (RuntimeException ex) {
    95  	    LogLog.warn("Failed to get value of property " + name);
    96        }
    97      }
    98    }
    99
    100   protected
    101   boolean isHandledType(Class type) {
    102     return String.class.isAssignableFrom(type) ||
    103       Integer.TYPE.isAssignableFrom(type) ||
    104       Long.TYPE.isAssignableFrom(type)    ||
    105       Boolean.TYPE.isAssignableFrom(type) ||
    106       Priority.class.isAssignableFrom(type);
    107   }
    108 }