Package org.apache.nutch.metadata
Class MetaWrapper
- java.lang.Object
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- org.apache.hadoop.io.GenericWritable
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- org.apache.nutch.util.GenericWritableConfigurable
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- org.apache.nutch.crawl.NutchWritable
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- org.apache.nutch.metadata.MetaWrapper
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- All Implemented Interfaces:
Configurable,Writable
public class MetaWrapper extends NutchWritable
This is a simple decorator that adds metadata to any Writable-s that can be serialized byNutchWritable. This is useful when data needs to be temporarily enriched during processing, but this temporary metadata doesn't need to be permanently stored after the job is done.- Author:
- Andrzej Bialecki
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Constructor Summary
Constructors Constructor Description MetaWrapper()MetaWrapper(Writable instance, Configuration conf)MetaWrapper(Metadata metadata, Writable instance, Configuration conf)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description voidaddMeta(String name, String value)Add metadata.StringgetMeta(String name)Get metadata value for a given key.MetadatagetMetadata()Get all metadata.String[]getMetaValues(String name)Get multiple metadata values for a given key.voidreadFields(DataInput in)voidsetMeta(String name, String value)Set metadata.voidwrite(DataOutput out)-
Methods inherited from class org.apache.nutch.crawl.NutchWritable
getTypes
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Methods inherited from class org.apache.nutch.util.GenericWritableConfigurable
getConf, setConf
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Methods inherited from class org.apache.hadoop.io.GenericWritable
get, set, toString
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Constructor Detail
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MetaWrapper
public MetaWrapper()
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MetaWrapper
public MetaWrapper(Writable instance, Configuration conf)
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MetaWrapper
public MetaWrapper(Metadata metadata, Writable instance, Configuration conf)
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Method Detail
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addMeta
public void addMeta(String name, String value)
Add metadata.- Parameters:
name- metadata name to addvalue- metadata value to add- See Also:
Metadata.add(String, String)
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setMeta
public void setMeta(String name, String value)
Set metadata.- Parameters:
name- metadata key to setvalue- metadata value to set- See Also:
Metadata.set(String, String)
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getMeta
public String getMeta(String name)
Get metadata value for a given key.- Parameters:
name- key to retrieve a value for- Returns:
- metadata value
- See Also:
Metadata.getValues(String)
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getMetaValues
public String[] getMetaValues(String name)
Get multiple metadata values for a given key.- Parameters:
name- key to retrieve values for- Returns:
- a string array containing metadata values
- See Also:
Metadata.getValues(String)
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readFields
public void readFields(DataInput in) throws IOException
- Specified by:
readFieldsin interfaceWritable- Overrides:
readFieldsin classGenericWritableConfigurable- Throws:
IOException
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write
public void write(DataOutput out) throws IOException
- Specified by:
writein interfaceWritable- Overrides:
writein classGenericWritable- Throws:
IOException
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