Configuration (Hadoop 1.2.2-SNAPSHOT API)

java.lang.Object
- org.apache.hadoop.conf.Configuration

所有已实现的接口:

Iterable<Map.Entry<String,String>>, Writable

直接已知子类:

JobConf
```
public class Configuration
extends Object
implements Iterable<Map.Entry<String,String>>, Writable
```
Provides access to configuration parameters.
Resources

Configurations are specified by resources. A resource contains a set of name/value pairs as XML data. Each resource is named by either a String or by a Path. If named by a String, then the classpath is examined for a file with that name. If named by a Path, then the local filesystem is examined directly, without referring to the classpath.
Unless explicitly turned off, Hadoop by default specifies two resources, loaded in-order from the classpath:
1. core-default.xml: Read-only defaults for hadoop.
2. core-site.xml: Site-specific configuration for a given hadoop installation.
Applications may add additional resources, which are loaded subsequent to these resources in the order they are added.
Final Parameters

Configuration parameters may be declared final. Once a resource declares a value final, no subsequently-loaded resource can alter that value. For example, one might define a final parameter with:
```
 <property>
 <name>dfs.client.buffer.dir</name>
 <value>/tmp/hadoop/dfs/client</value>
 <final>true</final>
 </property>
```
Administrators typically define parameters as final in core-site.xml for values that user applications may not alter.
Variable Expansion

Value strings are first processed for variable expansion. The available properties are:
1. Other properties defined in this Configuration; and, if a name is undefined here,
2. Properties in System.getProperties().
For example, if a configuration resource contains the following property definitions:
```
 <property>
 <name>basedir</name>
 <value>/user/${user.name}</value>
 </property>
 
 <property>
 <name>tempdir</name>
 <value>${basedir}/tmp</value>
 </property>
```
When conf.get("tempdir") is called, then ${basedir} will be resolved to another property in this Configuration, while ${user.name} would then ordinarily be resolved to the value of the System property with that name.

嵌套类概要

嵌套类
限定符和类型类和说明

static class Configuration.IntegerRanges
A class that represents a set of positive integer ranges.

嵌套类
限定符和类型	类和说明
`static class`	`Configuration.IntegerRanges` A class that represents a set of positive integer ranges.

构造器概要

构造器
构造器和说明
`Configuration()` A new configuration.
`Configuration(boolean loadDefaults)` A new configuration where the behavior of reading from the default resources can be turned off.
`Configuration(Configuration other)` A new configuration with the same settings cloned from another.

方法概要

方法
限定符和类型	方法和说明
`static void`	`addDefaultResource(String name)` Add a default resource.
`void`	`addResource(InputStream in)` Add a configuration resource.
`void`	`addResource(Path file)` Add a configuration resource.
`void`	`addResource(String name)` Add a configuration resource.
`void`	`addResource(URL url)` Add a configuration resource.
`void`	`clear()` Clears all keys from the configuration.
`static void`	`dumpConfiguration(Configuration config, Writer out)` Writes out all the parameters and their properties (final and resource) to the given `Writer` The format of the output would be { "properties" : [ {key1,value1,key1.isFinal,key1.resource}, {key2,value2, key2.isFinal,key2.resource}... ] } It does not output the parameters of the configuration object which is loaded from an input stream.
`String`	`get(String name)` Get the value of the `name` property, `null` if no such property exists.
`String`	`get(String name, String defaultValue)` Get the value of the `name` property.
`boolean`	`getBoolean(String name, boolean defaultValue)` Get the value of the `name` property as a `boolean`.
`Class<?>`	`getClass(String name, Class<?> defaultValue)` Get the value of the `name` property as a `Class`.
`<U> Class<? extends U>`	`getClass(String name, Class<? extends U> defaultValue, Class<U> xface)` Get the value of the `name` property as a `Class` implementing the interface specified by `xface`.
`Class<?>`	`getClassByName(String name)` Load a class by name.
`Class<?>[]`	`getClasses(String name, Class<?>... defaultValue)` Get the value of the `name` property as an array of `Class`.
`ClassLoader`	`getClassLoader()` Get the `ClassLoader` for this job.
`InputStream`	`getConfResourceAsInputStream(String name)` Get an input stream attached to the configuration resource with the given `name`.
`Reader`	`getConfResourceAsReader(String name)` Get a `Reader` attached to the configuration resource with the given `name`.
`<T extends Enum<T>> T`	`getEnum(String name, T defaultValue)` Return value matching this enumerated type.
`File`	`getFile(String dirsProp, String path)` Get a local file name under a directory named in dirsProp with the given path.
`float`	`getFloat(String name, float defaultValue)` Get the value of the `name` property as a `float`.
`<U> List<U>`	`getInstances(String name, Class<U> xface)` Get the value of the `name` property as a `List` of objects implementing the interface specified by `xface`.
`int`	`getInt(String name, int defaultValue)` Get the value of the `name` property as an `int`.
`Path`	`getLocalPath(String dirsProp, String path)` Get a local file under a directory named by dirsProp with the given path.
`long`	`getLong(String name, long defaultValue)` Get the value of the `name` property as a `long`.
`Configuration.IntegerRanges`	`getRange(String name, String defaultValue)` Parse the given attribute as a set of integer ranges
`String`	`getRaw(String name)` Get the value of the `name` property, without doing variable expansion.
`URL`	`getResource(String name)` Get the `URL` for the named resource.
`Collection<String>`	`getStringCollection(String name)` Get the comma delimited values of the `name` property as a collection of `String`s.
`String[]`	`getStrings(String name)` Get the comma delimited values of the `name` property as an array of `String`s.
`String[]`	`getStrings(String name, String... defaultValue)` Get the comma delimited values of the `name` property as an array of `String`s.
`Map<String,String>`	`getValByRegex(String regex)` get keys matching the the regex
`Iterator<Map.Entry<String,String>>`	`iterator()` Get an `Iterator` to go through the list of `String` key-value pairs in the configuration.
`static void`	`main(String[] args)` For debugging.
`void`	`readFields(DataInput in)` Deserialize the fields of this object from `in`.
`void`	`reloadConfiguration()` Reload configuration from previously added resources.
`void`	`set(String name, String value)` Set the `value` of the `name` property.
`void`	`setBoolean(String name, boolean value)` Set the value of the `name` property to a `boolean`.
`void`	`setBooleanIfUnset(String name, boolean value)` Set the given property, if it is currently unset.
`void`	`setClass(String name, Class<?> theClass, Class<?> xface)` Set the value of the `name` property to the name of a `theClass` implementing the given interface `xface`.
`void`	`setClassLoader(ClassLoader classLoader)` Set the class loader that will be used to load the various objects.
`<T extends Enum<T>> void`	`setEnum(String name, T value)` Set the value of the `name` property to the given type.
`void`	`setFloat(String name, float value)` Set the value of the `name` property to a `float`.
`void`	`setIfUnset(String name, String value)` Sets a property if it is currently unset.
`void`	`setInt(String name, int value)` Set the value of the `name` property to an `int`.
`void`	`setLong(String name, long value)` Set the value of the `name` property to a `long`.
`void`	`setQuietMode(boolean quietmode)` Set the quietness-mode.
`void`	`setStrings(String name, String... values)` Set the array of string values for the `name` property as as comma delimited values.
`int`	`size()` Return the number of keys in the configuration.
`String`	`toString()`
`void`	`unset(String name)` Unset a previously set property.
`void`	`write(DataOutput out)` Serialize the fields of this object to `out`.
`void`	`writeXml(OutputStream out)` Write out the non-default properties in this configuration to the given `OutputStream`.
`void`	`writeXml(Writer out)` Write out the non-default properties in this configuration to the given `Writer`.

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- 构造器详细资料
 - Configuration
```
public Configuration()
```
 A new configuration.
 - Configuration
```
public Configuration(boolean loadDefaults)
```
 A new configuration where the behavior of reading from the default resources can be turned off. If the parameter loadDefaults is false, the new instance will not load resources from the default files.
 
 参数:
 loadDefaults - specifies whether to load from the default files
 - Configuration
```
public Configuration(Configuration other)
```
 A new configuration with the same settings cloned from another.
 
 参数:
 other - the configuration from which to clone settings.
- 方法详细资料
 - addDefaultResource
```
public static void addDefaultResource(String name)
```
 Add a default resource. Resources are loaded in the order of the resources added.
 
 参数:
 name - file name. File should be present in the classpath.
 - addResource
```
public void addResource(String name)
```
 Add a configuration resource. The properties of this resource will override properties of previously added resources, unless they were marked final.
 
 参数:
 name - resource to be added, the classpath is examined for a file with that name.
 - addResource
```
public void addResource(URL url)
```
 Add a configuration resource. The properties of this resource will override properties of previously added resources, unless they were marked final.
 
 参数:
 url - url of the resource to be added, the local filesystem is examined directly to find the resource, without referring to the classpath.
 - addResource
```
public void addResource(Path file)
```
 Add a configuration resource. The properties of this resource will override properties of previously added resources, unless they were marked final.
 
 参数:
 file - file-path of resource to be added, the local filesystem is examined directly to find the resource, without referring to the classpath.
 - addResource
```
public void addResource(InputStream in)
```
 Add a configuration resource. The properties of this resource will override properties of previously added resources, unless they were marked final.
 
 参数:
 in - InputStream to deserialize the object from.
 - reloadConfiguration
```
public void reloadConfiguration()
```
 Reload configuration from previously added resources. This method will clear all the configuration read from the added resources, and final parameters. This will make the resources to be read again before accessing the values. Values that are added via set methods will overlay values read from the resources.
 - get
```
public String get(String name)
```
 Get the value of the name property, null if no such property exists. Values are processed for variable expansion before being returned.
 
 参数:
 name - the property name.
 
 返回:
 the value of the name property, or null if no such property exists.
 - getRaw
```
public String getRaw(String name)
```
 Get the value of the name property, without doing variable expansion.
 
 参数:
 name - the property name.
 
 返回:
 the value of the name property, or null if no such property exists.
 - set
```
public void set(String name,
 String value)
```
 Set the value of the name property.
 
 参数:
 name - property name.
 value - property value.
 - unset
```
public void unset(String name)
```
 Unset a previously set property.
 - setIfUnset
```
public void setIfUnset(String name,
 String value)
```
 Sets a property if it is currently unset.
 
 参数:
 name - the property name
 value - the new value
 - get
```
public String get(String name,
 String defaultValue)
```
 Get the value of the name property. If no such property exists, then defaultValue is returned.
 
 参数:
 name - property name.
 defaultValue - default value.
 
 返回:
 property value, or defaultValue if the property doesn't exist.
 - getInt
```
public int getInt(String name,
 int defaultValue)
```
 Get the value of the name property as an int. If no such property exists, or if the specified value is not a valid int, then defaultValue is returned.
 
 参数:
 name - property name.
 defaultValue - default value.
 
 返回:
 property value as an int, or defaultValue.
 - setInt
```
public void setInt(String name,
 int value)
```
 Set the value of the name property to an int.
 
 参数:
 name - property name.
 value - int value of the property.
 - getLong
```
public long getLong(String name,
 long defaultValue)
```
 Get the value of the name property as a long. If no such property is specified, or if the specified value is not a valid long, then defaultValue is returned.
 
 参数:
 name - property name.
 defaultValue - default value.
 
 返回:
 property value as a long, or defaultValue.
 - setLong
```
public void setLong(String name,
 long value)
```
 Set the value of the name property to a long.
 
 参数:
 name - property name.
 value - long value of the property.
 - getFloat
```
public float getFloat(String name,
 float defaultValue)
```
 Get the value of the name property as a float. If no such property is specified, or if the specified value is not a valid float, then defaultValue is returned.
 
 参数:
 name - property name.
 defaultValue - default value.
 
 返回:
 property value as a float, or defaultValue.
 - setFloat
```
public void setFloat(String name,
 float value)
```
 Set the value of the name property to a float.
 
 参数:
 name - property name.
 value - property value.
 - getBoolean
```
public boolean getBoolean(String name,
 boolean defaultValue)
```
 Get the value of the name property as a boolean. If no such property is specified, or if the specified value is not a valid boolean, then defaultValue is returned.
 
 参数:
 name - property name.
 defaultValue - default value.
 
 返回:
 property value as a boolean, or defaultValue.
 - setBoolean
```
public void setBoolean(String name,
 boolean value)
```
 Set the value of the name property to a boolean.
 
 参数:
 name - property name.
 value - boolean value of the property.
 - setBooleanIfUnset
```
public void setBooleanIfUnset(String name,
 boolean value)
```
 Set the given property, if it is currently unset.
 
 参数:
 name - property name
 value - new value
 - setEnum
```
public <T extends Enum<T>> void setEnum(String name,
 T value)
```
 Set the value of the name property to the given type. This is equivalent to set(<name>, value.toString()).
 
 参数:
 name - property name
 value - new value
 - getEnum
```
public <T extends Enum<T>> T getEnum(String name,
 T defaultValue)
```
 Return value matching this enumerated type.
 
 参数:
 name - Property name
 defaultValue - Value returned if no mapping exists
 
 抛出:
 
 IllegalArgumentException - If mapping is illegal for the type provided
 - getRange
```
public Configuration.IntegerRanges getRange(String name,
 String defaultValue)
```
 Parse the given attribute as a set of integer ranges
 
 参数:
 name - the attribute name
 defaultValue - the default value if it is not set
 
 返回:
 a new set of ranges from the configured value
 - getStringCollection
```
public Collection<String> getStringCollection(String name)
```
 Get the comma delimited values of the name property as a collection of Strings. If no such property is specified then empty collection is returned.
 This is an optimized version of getStrings(String)
 
 参数:
 name - property name.
 
 返回:
 property value as a collection of Strings.
 - getStrings
```
public String[] getStrings(String name)
```
 Get the comma delimited values of the name property as an array of Strings. If no such property is specified then null is returned.
 
 参数:
 name - property name.
 
 返回:
 property value as an array of Strings, or null.
 - getStrings
```
public String[] getStrings(String name,
 String... defaultValue)
```
 Get the comma delimited values of the name property as an array of Strings. If no such property is specified then default value is returned.
 
 参数:
 name - property name.
 defaultValue - The default value
 
 返回:
 property value as an array of Strings, or default value.
 - setStrings
```
public void setStrings(String name,
 String... values)
```
 Set the array of string values for the name property as as comma delimited values.
 
 参数:
 name - property name.
 values - The values
 - getClassByName
```
public Class<?> getClassByName(String name)
 throws ClassNotFoundException
```
 Load a class by name.
 
 参数:
 name - the class name.
 
 返回:
 the class object.
 
 抛出:
 
 ClassNotFoundException - if the class is not found.
 - getClasses
```
public Class<?>[] getClasses(String name,
 Class<?>... defaultValue)
```
 Get the value of the name property as an array of Class. The value of the property specifies a list of comma separated class names. If no such property is specified, then defaultValue is returned.
 
 参数:
 name - the property name.
 defaultValue - default value.
 
 返回:
 property value as a Class[], or defaultValue.
 - getClass
```
public Class<?> getClass(String name,
 Class<?> defaultValue)
```
 Get the value of the name property as a Class. If no such property is specified, then defaultValue is returned.
 
 参数:
 name - the class name.
 defaultValue - default value.
 
 返回:
 property value as a Class, or defaultValue.
 - getClass
```
public  Class<? extends U> getClass(String name,
 Class<? extends U> defaultValue,
 Class xface)
```
 Get the value of the name property as a Class implementing the interface specified by xface. If no such property is specified, then defaultValue is returned. An exception is thrown if the returned class does not implement the named interface.
 
 参数:
 name - the class name.
 defaultValue - default value.
 xface - the interface implemented by the named class.
 
 返回:
 property value as a Class, or defaultValue.
 - getInstances
```
public  List getInstances(String name,
 Class xface)
```
 Get the value of the name property as a List of objects implementing the interface specified by xface. An exception is thrown if any of the classes does not exist, or if it does not implement the named interface.
 
 参数:
 name - the property name.
 xface - the interface implemented by the classes named by name.
 
 返回:
 a List of objects implementing xface.
 - setClass
```
public void setClass(String name,
 Class<?> theClass,
 Class<?> xface)
```
 Set the value of the name property to the name of a theClass implementing the given interface xface. An exception is thrown if theClass does not implement the interface xface.
 
 参数:
 name - property name.
 theClass - property value.
 xface - the interface implemented by the named class.
 - getLocalPath
```
public Path getLocalPath(String dirsProp,
 String path)
 throws IOException
```
 Get a local file under a directory named by dirsProp with the given path. If dirsProp contains multiple directories, then one is chosen based on path's hash code. If the selected directory does not exist, an attempt is made to create it.
 
 参数:
 dirsProp - directory in which to locate the file.
 path - file-path.
 
 返回:
 local file under the directory with the given path.
 
 抛出:
 
 IOException
 - getFile
```
public File getFile(String dirsProp,
 String path)
 throws IOException
```
 Get a local file name under a directory named in dirsProp with the given path. If dirsProp contains multiple directories, then one is chosen based on path's hash code. If the selected directory does not exist, an attempt is made to create it.
 
 参数:
 dirsProp - directory in which to locate the file.
 path - file-path.
 
 返回:
 local file under the directory with the given path.
 
 抛出:
 
 IOException
 - getResource
```
public URL getResource(String name)
```
 Get the URL for the named resource.
 
 参数:
 name - resource name.
 
 返回:
 the url for the named resource.
 - getConfResourceAsInputStream
```
public InputStream getConfResourceAsInputStream(String name)
```
 Get an input stream attached to the configuration resource with the given name.
 
 参数:
 name - configuration resource name.
 
 返回:
 an input stream attached to the resource.
 - getConfResourceAsReader
```
public Reader getConfResourceAsReader(String name)
```
 Get a Reader attached to the configuration resource with the given name.
 
 参数:
 name - configuration resource name.
 
 返回:
 a reader attached to the resource.
 - size
```
public int size()
```
 Return the number of keys in the configuration.
 
 返回:
 number of keys in the configuration.
 - clear
```
public void clear()
```
 Clears all keys from the configuration.
 - iterator
```
public Iterator<Map.Entry<String,String>> iterator()
```
 Get an Iterator to go through the list of String key-value pairs in the configuration.
 
 指定者:
 
 iterator 在接口中 Iterable<Map.Entry<String,String>>
 
 返回:
 an iterator over the entries.
 - writeXml
```
public void writeXml(OutputStream out)
 throws IOException
```
 Write out the non-default properties in this configuration to the given OutputStream.
 
 参数:
 out - the output stream to write to.
 
 抛出:
 
 IOException
 - writeXml
```
public void writeXml(Writer out)
 throws IOException
```
 Write out the non-default properties in this configuration to the given Writer.
 
 参数:
 out - the writer to write to.
 
 抛出:
 
 IOException
 - dumpConfiguration
```
public static void dumpConfiguration(Configuration config,
 Writer out)
 throws IOException
```
 Writes out all the parameters and their properties (final and resource) to the given Writer The format of the output would be { "properties" : [ {key1,value1,key1.isFinal,key1.resource}, {key2,value2, key2.isFinal,key2.resource}... ] } It does not output the parameters of the configuration object which is loaded from an input stream.
 
 参数:
 out - the Writer to write to
 
 抛出:
 
 IOException
 - getClassLoader
```
public ClassLoader getClassLoader()
```
 Get the ClassLoader for this job.
 
 返回:
 the correct class loader.
 - setClassLoader
```
public void setClassLoader(ClassLoader classLoader)
```
 Set the class loader that will be used to load the various objects.
 
 参数:
 classLoader - the new class loader.
 - toString
```
public String toString()
```
 覆盖:
 
 toString 在类中 Object
 - setQuietMode
```
public void setQuietMode(boolean quietmode)
```
 Set the quietness-mode. In the quiet-mode, error and informational messages might not be logged.
 
 参数:
 quietmode - true to set quiet-mode on, false to turn it off.
 - main
```
public static void main(String[] args)
 throws Exception
```
 For debugging. List non-default properties to the terminal and exit.
 
 抛出:
 
 Exception
 - readFields
```
public void readFields(DataInput in)
 throws IOException
```
 从接口复制的说明: Writable
 
 Deserialize the fields of this object from in.
 For efficiency, implementations should attempt to re-use storage in the existing object where possible.
 
 指定者:
 
 readFields 在接口中 Writable
 
 参数:
 in - DataInput to deseriablize this object from.
 
 抛出:
 
 IOException
 - write
```
public void write(DataOutput out)
 throws IOException
```
 从接口复制的说明: Writable
 
 Serialize the fields of this object to out.
 
 指定者:
 
 write 在接口中 Writable
 
 参数:
 out - DataOuput to serialize this object into.
 
 抛出:
 
 IOException
 - getValByRegex
```
public Map<String,String> getValByRegex(String regex)
```
 get keys matching the the regex
 
 参数:
 regex -
 
 返回:
 Map with matching keys

类 Configuration

Resources

Final Parameters

Variable Expansion

嵌套类概要

构造器概要

方法概要

从类继承的方法 java.lang.Object

构造器详细资料

Configuration

Configuration

Configuration

方法详细资料

addDefaultResource

addResource

addResource

addResource

addResource

reloadConfiguration

get

getRaw

set

unset

setIfUnset

get

getInt

setInt

getLong

setLong

getFloat

setFloat

getBoolean

setBoolean

setBooleanIfUnset

setEnum

getEnum

getRange

getStringCollection

getStrings

getStrings

setStrings

getClassByName

getClasses

getClass

getClass

getInstances

setClass

getLocalPath

getFile

getResource

getConfResourceAsInputStream

getConfResourceAsReader

size

clear

iterator

writeXml

writeXml

dumpConfiguration

getClassLoader

setClassLoader

toString

setQuietMode

main

readFields

write

getValByRegex