[120] | 1 | /* |
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| 2 | * ContextFactory.java |
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| 3 | * |
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| 4 | * Licensed to the Apache Software Foundation (ASF) under one |
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| 5 | * or more contributor license agreements. See the NOTICE file |
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| 6 | * distributed with this work for additional information |
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| 7 | * regarding copyright ownership. The ASF licenses this file |
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| 8 | * to you under the Apache License, Version 2.0 (the |
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| 9 | * "License"); you may not use this file except in compliance |
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| 10 | * with the License. You may obtain a copy of the License at |
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| 11 | * |
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| 12 | * http://www.apache.org/licenses/LICENSE-2.0 |
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| 13 | * |
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| 14 | * Unless required by applicable law or agreed to in writing, software |
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| 15 | * distributed under the License is distributed on an "AS IS" BASIS, |
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| 16 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 17 | * See the License for the specific language governing permissions and |
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| 18 | * limitations under the License. |
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| 19 | */ |
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| 20 | |
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| 21 | package org.apache.hadoop.metrics; |
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| 22 | |
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| 23 | import java.io.IOException; |
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| 24 | import java.io.InputStream; |
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| 25 | import java.util.HashMap; |
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| 26 | import java.util.Iterator; |
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| 27 | import java.util.Map; |
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| 28 | import java.util.Properties; |
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| 29 | import org.apache.hadoop.metrics.spi.AbstractMetricsContext; |
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| 30 | import org.apache.hadoop.metrics.spi.NullContext; |
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| 31 | |
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| 32 | /** |
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| 33 | * Factory class for creating MetricsContext objects. To obtain an instance |
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| 34 | * of this class, use the static <code>getFactory()</code> method. |
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| 35 | */ |
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| 36 | public class ContextFactory { |
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| 37 | |
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| 38 | private static final String PROPERTIES_FILE = |
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| 39 | "/hadoop-metrics.properties"; |
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| 40 | private static final String CONTEXT_CLASS_SUFFIX = |
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| 41 | ".class"; |
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| 42 | private static final String DEFAULT_CONTEXT_CLASSNAME = |
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| 43 | "org.apache.hadoop.metrics.spi.NullContext"; |
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| 44 | |
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| 45 | private static ContextFactory theFactory = null; |
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| 46 | |
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| 47 | private Map<String,Object> attributeMap = new HashMap<String,Object>(); |
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| 48 | private Map<String,MetricsContext> contextMap = |
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| 49 | new HashMap<String,MetricsContext>(); |
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| 50 | |
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| 51 | // Used only when contexts, or the ContextFactory itself, cannot be |
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| 52 | // created. |
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| 53 | private static Map<String,MetricsContext> nullContextMap = |
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| 54 | new HashMap<String,MetricsContext>(); |
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| 55 | |
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| 56 | /** Creates a new instance of ContextFactory */ |
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| 57 | protected ContextFactory() { |
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| 58 | } |
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| 59 | |
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| 60 | /** |
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| 61 | * Returns the value of the named attribute, or null if there is no |
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| 62 | * attribute of that name. |
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| 63 | * |
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| 64 | * @param attributeName the attribute name |
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| 65 | * @return the attribute value |
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| 66 | */ |
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| 67 | public Object getAttribute(String attributeName) { |
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| 68 | return attributeMap.get(attributeName); |
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| 69 | } |
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| 70 | |
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| 71 | /** |
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| 72 | * Returns the names of all the factory's attributes. |
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| 73 | * |
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| 74 | * @return the attribute names |
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| 75 | */ |
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| 76 | public String[] getAttributeNames() { |
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| 77 | String[] result = new String[attributeMap.size()]; |
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| 78 | int i = 0; |
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| 79 | // for (String attributeName : attributeMap.keySet()) { |
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| 80 | Iterator it = attributeMap.keySet().iterator(); |
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| 81 | while (it.hasNext()) { |
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| 82 | result[i++] = (String) it.next(); |
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| 83 | } |
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| 84 | return result; |
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| 85 | } |
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| 86 | |
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| 87 | /** |
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| 88 | * Sets the named factory attribute to the specified value, creating it |
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| 89 | * if it did not already exist. If the value is null, this is the same as |
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| 90 | * calling removeAttribute. |
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| 91 | * |
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| 92 | * @param attributeName the attribute name |
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| 93 | * @param value the new attribute value |
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| 94 | */ |
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| 95 | public void setAttribute(String attributeName, Object value) { |
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| 96 | attributeMap.put(attributeName, value); |
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| 97 | } |
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| 98 | |
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| 99 | /** |
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| 100 | * Removes the named attribute if it exists. |
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| 101 | * |
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| 102 | * @param attributeName the attribute name |
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| 103 | */ |
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| 104 | public void removeAttribute(String attributeName) { |
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| 105 | attributeMap.remove(attributeName); |
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| 106 | } |
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| 107 | |
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| 108 | /** |
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| 109 | * Returns the named MetricsContext instance, constructing it if necessary |
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| 110 | * using the factory's current configuration attributes. <p/> |
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| 111 | * |
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| 112 | * When constructing the instance, if the factory property |
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| 113 | * <i>contextName</i>.class</code> exists, |
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| 114 | * its value is taken to be the name of the class to instantiate. Otherwise, |
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| 115 | * the default is to create an instance of |
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| 116 | * <code>org.apache.hadoop.metrics.spi.NullContext</code>, which is a |
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| 117 | * dummy "no-op" context which will cause all metric data to be discarded. |
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| 118 | * |
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| 119 | * @param contextName the name of the context |
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| 120 | * @return the named MetricsContext |
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| 121 | */ |
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| 122 | public synchronized MetricsContext getContext(String refName, String contextName) |
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| 123 | throws IOException, ClassNotFoundException, |
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| 124 | InstantiationException, IllegalAccessException { |
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| 125 | MetricsContext metricsContext = contextMap.get(refName); |
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| 126 | if (metricsContext == null) { |
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| 127 | String classNameAttribute = refName + CONTEXT_CLASS_SUFFIX; |
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| 128 | String className = (String) getAttribute(classNameAttribute); |
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| 129 | if (className == null) { |
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| 130 | className = DEFAULT_CONTEXT_CLASSNAME; |
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| 131 | } |
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| 132 | Class contextClass = Class.forName(className); |
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| 133 | metricsContext = (MetricsContext) contextClass.newInstance(); |
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| 134 | metricsContext.init(contextName, this); |
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| 135 | contextMap.put(contextName, metricsContext); |
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| 136 | } |
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| 137 | return metricsContext; |
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| 138 | } |
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| 139 | |
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| 140 | public synchronized MetricsContext getContext(String contextName) |
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| 141 | throws IOException, ClassNotFoundException, InstantiationException, |
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| 142 | IllegalAccessException { |
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| 143 | return getContext(contextName, contextName); |
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| 144 | } |
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| 145 | |
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| 146 | /** |
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| 147 | * Returns a "null" context - one which does nothing. |
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| 148 | */ |
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| 149 | public static synchronized MetricsContext getNullContext(String contextName) { |
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| 150 | MetricsContext nullContext = nullContextMap.get(contextName); |
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| 151 | if (nullContext == null) { |
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| 152 | nullContext = new NullContext(); |
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| 153 | nullContextMap.put(contextName, nullContext); |
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| 154 | } |
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| 155 | return nullContext; |
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| 156 | } |
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| 157 | |
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| 158 | /** |
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| 159 | * Returns the singleton ContextFactory instance, constructing it if |
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| 160 | * necessary. <p/> |
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| 161 | * |
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| 162 | * When the instance is constructed, this method checks if the file |
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| 163 | * <code>hadoop-metrics.properties</code> exists on the class path. If it |
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| 164 | * exists, it must be in the format defined by java.util.Properties, and all |
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| 165 | * the properties in the file are set as attributes on the newly created |
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| 166 | * ContextFactory instance. |
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| 167 | * |
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| 168 | * @return the singleton ContextFactory instance |
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| 169 | */ |
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| 170 | public static synchronized ContextFactory getFactory() throws IOException { |
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| 171 | if (theFactory == null) { |
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| 172 | theFactory = new ContextFactory(); |
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| 173 | theFactory.setAttributes(); |
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| 174 | } |
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| 175 | return theFactory; |
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| 176 | } |
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| 177 | |
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| 178 | private void setAttributes() throws IOException { |
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| 179 | InputStream is = getClass().getResourceAsStream(PROPERTIES_FILE); |
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| 180 | if (is != null) { |
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| 181 | Properties properties = new Properties(); |
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| 182 | properties.load(is); |
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| 183 | //for (Object propertyNameObj : properties.keySet()) { |
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| 184 | Iterator it = properties.keySet().iterator(); |
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| 185 | while (it.hasNext()) { |
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| 186 | String propertyName = (String) it.next(); |
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| 187 | String propertyValue = properties.getProperty(propertyName); |
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| 188 | setAttribute(propertyName, propertyValue); |
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| 189 | } |
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| 190 | } |
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| 191 | } |
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| 192 | |
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| 193 | } |
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