org.apache.pig.scripting
Class ScriptEngine

java.lang.Object
  org.apache.pig.scripting.ScriptEngine

Direct Known Subclasses:

JsScriptEngine, JythonScriptEngine

public abstract class ScriptEngine
extends Object

Base class for various scripting implementations

Nested Class Summary

static class

ScriptEngine.SupportedScriptLang

Field Summary

static String

NAMESPACE_SEPARATOR

Constructor Summary

ScriptEngine()

Method Summary

static ScriptEngine	getInstance(String scriptingLang) Gets instance of the scriptEngine for the given scripting language
static String	getJarPath(Class<?> clazz) Figures out the jar location from the class
protected abstract Map<String,Object>	getParamsFromVariables() Returns a map from local variable names to their values
protected Map<String,List<PigStats>>	getPigStatsMap() Gets the collection of PigStats after the script is run.
protected static InputStream	getScriptAsStream(String scriptPath) open a stream load a script locally or in the classpath
protected abstract String	getScriptingLang() Gets ScriptEngine classname or keyword for the scripting language
static ScriptEngine.SupportedScriptLang	getSupportedScriptLang(String file)
protected abstract Map<String,List<PigStats>>	main(PigContext context, String scriptFile) Actually runs the script file.
abstract void	registerFunctions(String path, String namespace, PigContext pigContext) Registers scripting language functions as Pig functions with given namespace
Map<String,List<PigStats>>	run(PigContext pigContext, String scriptFile) Runs a script file.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

NAMESPACE_SEPARATOR

public static final String NAMESPACE_SEPARATOR

See Also:

Constant Field Values

Constructor Detail

ScriptEngine

public ScriptEngine()

Method Detail

getScriptAsStream

protected static InputStream getScriptAsStream(String scriptPath)

open a stream load a script locally or in the classpath

Parameters:

scriptPath - the path of the script

Returns:

a stream (it is the responsibility of the caller to close it)

Throws:

IllegalStateException - if we could not open a stream

getSupportedScriptLang

public static ScriptEngine.SupportedScriptLang getSupportedScriptLang(String file)
                                                               throws IOException

Parameters:

file - the file to inspect

Returns:

the Supported Script Lang if this is a supported script language

Throws:

IOException - if there was an error reading the file or if the file defines explicitly an unknown #!

registerFunctions

public abstract void registerFunctions(String path,
                                       String namespace,
                                       PigContext pigContext)
                                throws IOException

Registers scripting language functions as Pig functions with given namespace

Parameters:

path - path of the script

namespace - namespace for the functions

pigContext - pigcontext to register functions to pig in the given namespace

Throws:

IOException

main

protected abstract Map<String,List<PigStats>> main(PigContext context,
                                                   String scriptFile)
                                            throws IOException

Actually runs the script file. This method will be implemented by individual script engines.

Parameters:

context - ScriptPigContext to run the script file

scriptFile - the file

Throws:

IOException

getScriptingLang

protected abstract String getScriptingLang()

Gets ScriptEngine classname or keyword for the scripting language

getParamsFromVariables

protected abstract Map<String,Object> getParamsFromVariables()
                                                      throws IOException

Returns a map from local variable names to their values

Throws:

IOException

getJarPath

public static String getJarPath(Class<?> clazz)
                         throws FileNotFoundException

Figures out the jar location from the class

Parameters:

clazz - class in the jar file

Returns:

the jar file location, null if the class was not loaded from a jar

Throws:

FileNotFoundException

getInstance

public static ScriptEngine getInstance(String scriptingLang)
                                throws IOException

Gets instance of the scriptEngine for the given scripting language

Parameters:

scriptingLang - ScriptEngine classname or keyword for the scriptingLang

Returns:

scriptengine for the given scripting language

Throws:

IOException

run

public Map<String,List<PigStats>> run(PigContext pigContext,
                                      String scriptFile)
                               throws ExecException,
                                      IOException

Runs a script file.

Parameters:

pigContext - PigContext to run the script file

scriptFile - the file

Returns:

a collection of PigStats objects. One for each runtime instance of Pig in the script. For named pipelines, the map key is the name of the pipeline. For unnamed pipeline, the map key is the script id associated with the instance.

Throws:

ExecException

IOException

getPigStatsMap

protected Map<String,List<PigStats>> getPigStatsMap()

Gets the collection of PigStats after the script is run.