org.apache.flume.Context Maven / Gradle / Ivy
/*
* 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.flume;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
/**
* The context is a key-value store used to pass configuration information
* throughout the system.
*/
public class Context {
private Map parameters;
public Context() {
parameters = Collections.synchronizedMap(new HashMap());
}
public Context(Map paramters) {
this();
this.putAll(paramters);
}
/**
* Gets a copy of the backing map structure.
* @return immutable copy of backing map structure
*/
public ImmutableMap getParameters() {
synchronized (parameters) {
return ImmutableMap.copyOf(parameters);
}
}
/**
* Removes all of the mappings from this map.
*/
public void clear() {
parameters.clear();
}
/**
* Get properties which start with a prefix. When a property is returned,
* the prefix is removed the from name. For example, if this method is
* called with a parameter "hdfs." and the context contains:
*
* { hdfs.key = value, otherKey = otherValue }
*
* this method will return a map containing:
*
* { key = value}
*
*
* Note: The prefix must end with a period character. If not
* this method will raise an IllegalArgumentException.
*
* @param prefix key prefix to find and remove from keys in resulting map
* @return map with keys which matched prefix with prefix removed from
* keys in resulting map. If no keys are matched, the returned map is
* empty
* @throws IllegalArguemntException if the given prefix does not end with
* a period character.
*/
public ImmutableMap getSubProperties(String prefix) {
Preconditions.checkArgument(prefix.endsWith("."),
"The given prefix does not end with a period (" + prefix + ")");
Map result = Maps.newHashMap();
synchronized (parameters) {
for (String key : parameters.keySet()) {
if (key.startsWith(prefix)) {
String name = key.substring(prefix.length());
result.put(name, parameters.get(key));
}
}
}
return ImmutableMap.copyOf(result);
}
/**
* Associates all of the given map's keys and values in the Context.
*/
public void putAll(Map map) {
parameters.putAll(map);
}
/**
* Associates the specified value with the specified key in this context.
* If the context previously contained a mapping for the key, the old value
* is replaced by the specified value.
* @param key key with which the specified value is to be associated
* @param value to be associated with the specified key
*/
public void put(String key, String value) {
parameters.put(key, value);
}
/**
* Returns true if this Context contains a mapping for key.
* Otherwise, returns false.
*/
public boolean containsKey(String key) {
return parameters.containsKey(key);
}
/**
* Gets value mapped to key, returning defaultValue if unmapped.
* @param key to be found
* @param defaultValue returned if key is unmapped
* @return value associated with key
*/
public Boolean getBoolean(String key, Boolean defaultValue) {
String value = get(key);
if (value != null) {
return Boolean.parseBoolean(value.trim());
}
return defaultValue;
}
/**
* Gets value mapped to key, returning null if unmapped.
*
* Note that this method returns an object as opposed to a
* primitive. The configuration key requested may not be mapped
* to a value and by returning the primitive object wrapper we can
* return null. If the key does not exist the return value of
* this method is assigned directly to a primitive, a
* {@link NullPointerException} will be thrown.
*
* @param key to be found
* @return value associated with key or null if unmapped
*/
public Boolean getBoolean(String key) {
return getBoolean(key, null);
}
/**
* Gets value mapped to key, returning defaultValue if unmapped.
* @param key to be found
* @param defaultValue returned if key is unmapped
* @return value associated with key
*/
public Integer getInteger(String key, Integer defaultValue) {
String value = get(key);
if (value != null) {
return Integer.parseInt(value.trim());
}
return defaultValue;
}
/**
* Gets value mapped to key, returning null if unmapped.
*
* Note that this method returns an object as opposed to a
* primitive. The configuration key requested may not be mapped
* to a value and by returning the primitive object wrapper we can
* return null. If the key does not exist the return value of
* this method is assigned directly to a primitive, a
* {@link NullPointerException} will be thrown.
*
* @param key to be found
* @return value associated with key or null if unmapped
*/
public Integer getInteger(String key) {
return getInteger(key, null);
}
/**
* Gets value mapped to key, returning defaultValue if unmapped.
* @param key to be found
* @param defaultValue returned if key is unmapped
* @return value associated with key
*/
public Long getLong(String key, Long defaultValue) {
String value = get(key);
if (value != null) {
return Long.parseLong(value.trim());
}
return defaultValue;
}
/**
* Gets value mapped to key, returning null if unmapped.
*
* Note that this method returns an object as opposed to a
* primitive. The configuration key requested may not be mapped
* to a value and by returning the primitive object wrapper we can
* return null. If the key does not exist the return value of
* this method is assigned directly to a primitive, a
* {@link NullPointerException} will be thrown.
*
* @param key to be found
* @return value associated with key or null if unmapped
*/
public Long getLong(String key) {
return getLong(key, null);
}
/**
* Gets value mapped to key, returning defaultValue if unmapped.
* @param key to be found
* @param defaultValue returned if key is unmapped
* @return value associated with key
*/
public String getString(String key, String defaultValue) {
return get(key, defaultValue);
}
/**
* Gets value mapped to key, returning null if unmapped.
* @param key to be found
* @return value associated with key or null if unmapped
*/
public String getString(String key) {
return get(key);
}
private String get(String key, String defaultValue) {
String result = parameters.get(key);
if (result != null) {
return result;
}
return defaultValue;
}
private String get(String key) {
return get(key, null);
}
@Override
public String toString() {
return "{ parameters:" + parameters + " }";
}
}