Interface ScriptEngine

All Known Implementing Classes:

AbstractScriptEngine

public interface ScriptEngine

ScriptEngine is the fundamental interface whose methods must be fully functional in every implementation of this specification.

These methods provide basic scripting functionality. Applications written to this simple interface are expected to work with minimal modifications in every implementation. It includes methods that execute scripts, and ones that set and get values.

The values are key/value pairs of two types. The first type of pairs consists of those whose keys are reserved and defined in this specification or by individual implementations. The values in the pairs with reserved keys have specified meanings.

The other type of pairs consists of those that create Java language Bindings, the values are usually represented in scripts by the corresponding keys or by decorated forms of them.

Since:

1.6

Fields

ARGV

static final String ARGV

Reserved key for a named value that passes an array of positional arguments to a script.

FILENAME

static final String FILENAME

Reserved key for a named value that is the name of the file being executed.

ENGINE

static final String ENGINE

Reserved key for a named value that is the name of the ScriptEngine implementation.

ENGINE_VERSION

static final String ENGINE_VERSION

Reserved key for a named value that identifies the version of the ScriptEngine implementation.

NAME

static final String NAME

Reserved key for a named value that identifies the short name of the scripting language. The name is used by the ScriptEngineManager to locate a ScriptEngine with a given name in the getEngineByName method.

LANGUAGE

static final String LANGUAGE

Reserved key for a named value that is the full name of Scripting Language supported by the implementation.

LANGUAGE_VERSION

static final String LANGUAGE_VERSION

Reserved key for the named value that identifies the version of the scripting language supported by the implementation.

Methods

eval

Object eval(String script,
            ScriptContext context)
     throws ScriptException

Causes the immediate execution of the script whose source is the String passed as the first argument. The script may be reparsed or recompiled before execution. State left in the engine from previous executions, including variable values and compiled procedures may be visible during this execution.

Parameters:

script - The script to be executed by the script engine.

context - A ScriptContext exposing sets of attributes in different scopes. The meanings of the scopes ScriptContext.GLOBAL_SCOPE, and ScriptContext.ENGINE_SCOPE are defined in the specification.

The ENGINE_SCOPE Bindings of the ScriptContext contains the bindings of scripting variables to application objects to be used during this script execution.

Returns:

The value returned from the execution of the script.

Throws:

ScriptException - if an error occurs in script. ScriptEngines should create and throw ScriptException wrappers for checked Exceptions thrown by underlying scripting implementations.

NullPointerException - if either argument is null.

eval

Object eval(Reader reader,
            ScriptContext context)
     throws ScriptException

Same as eval(String, ScriptContext) where the source of the script is read from a Reader.

Parameters:

reader - The source of the script to be executed by the script engine.

context - The ScriptContext passed to the script engine.

Returns:

The value returned from the execution of the script.

Throws:

ScriptException - if an error occurs in script.

NullPointerException - if either argument is null.

eval

Object eval(String script)
     throws ScriptException

Executes the specified script. The default ScriptContext for the ScriptEngine is used.

Parameters:

script - The script language source to be executed.

Returns:

The value returned from the execution of the script.

Throws:

ScriptException - if error occurs in script.

NullPointerException - if the argument is null.

eval

Object eval(Reader reader)
     throws ScriptException

Same as eval(String) except that the source of the script is provided as a Reader

Parameters:

reader - The source of the script.

Returns:

The value returned by the script.

Throws:

ScriptException - if an error occurs in script.

NullPointerException - if the argument is null.

eval

Object eval(String script,
            Bindings n)
     throws ScriptException

Executes the script using the Bindings argument as the ENGINE_SCOPE Bindings of the ScriptEngine during the script execution. The Reader, Writer and non-ENGINE_SCOPE Bindings of the default ScriptContext are used. The ENGINE_SCOPE Bindings of the ScriptEngine is not changed, and its mappings are unaltered by the script execution.

Parameters:

script - The source for the script.

n - The Bindings of attributes to be used for script execution.

Returns:

The value returned by the script.

Throws:

ScriptException - if an error occurs in script.

NullPointerException - if either argument is null.

eval

Object eval(Reader reader,
            Bindings n)
     throws ScriptException

Same as eval(String, Bindings) except that the source of the script is provided as a Reader.

Parameters:

reader - The source of the script.

n - The Bindings of attributes.

Returns:

The value returned by the script.

Throws:

ScriptException - if an error occurs.

NullPointerException - if either argument is null.

put

void put(String key,
         Object value)

Sets a key/value pair in the state of the ScriptEngine that may either create a Java Language Binding to be used in the execution of scripts or be used in some other way, depending on whether the key is reserved. Must have the same effect as getBindings(ScriptContext.ENGINE_SCOPE).put.

Parameters:

key - The name of named value to add

value - The value of named value to add.

Throws:

NullPointerException - if key is null.

IllegalArgumentException - if key is empty.

get

Object get(String key)

Retrieves a value set in the state of this engine. The value might be one which was set using setValue or some other value in the state of the ScriptEngine, depending on the implementation. Must have the same effect as getBindings(ScriptContext.ENGINE_SCOPE).get

Parameters:

key - The key whose value is to be returned

Returns:

the value for the given key

Throws:

NullPointerException - if key is null.

IllegalArgumentException - if key is empty.

getBindings

Bindings getBindings(int scope)

Returns a scope of named values. The possible scopes are:

• ScriptContext.GLOBAL_SCOPE - The set of named values representing global scope. If this ScriptEngine is created by a ScriptEngineManager, then the manager sets global scope bindings. This may be null if no global scope is associated with this ScriptEngine
• ScriptContext.ENGINE_SCOPE - The set of named values representing the state of this ScriptEngine. The values are generally visible in scripts using the associated keys as variable names.
• Any other value of scope defined in the default ScriptContext of the ScriptEngine.

The Bindings instances that are returned must be identical to those returned by the getBindings method of ScriptContext called with corresponding arguments on the default ScriptContext of the ScriptEngine.

Parameters:

scope - Either ScriptContext.ENGINE_SCOPE or ScriptContext.GLOBAL_SCOPE which specifies the Bindings to return. Implementations of ScriptContext may define additional scopes. If the default ScriptContext of the ScriptEngine defines additional scopes, any of them can be passed to get the corresponding Bindings.

Returns:

The Bindings with the specified scope.

Throws:

IllegalArgumentException - if specified scope is invalid

setBindings

void setBindings(Bindings bindings,
                 int scope)

Sets a scope of named values to be used by scripts. The possible scopes are:

• ScriptContext.ENGINE_SCOPE - The specified Bindings replaces the engine scope of the ScriptEngine.
• ScriptContext.GLOBAL_SCOPE - The specified Bindings must be visible as the GLOBAL_SCOPE.
• Any other value of scope defined in the default ScriptContext of the ScriptEngine.

The method must have the same effect as calling the setBindings method of ScriptContext with the corresponding value of scope on the default ScriptContext of the ScriptEngine.

Parameters:

bindings - The Bindings for the specified scope.

scope - The specified scope. Either ScriptContext.ENGINE_SCOPE, ScriptContext.GLOBAL_SCOPE, or any other valid value of scope.

Throws:

IllegalArgumentException - if the scope is invalid

NullPointerException - if the bindings is null and the scope is ScriptContext.ENGINE_SCOPE

createBindings

Bindings createBindings()

Returns an uninitialized Bindings.

Returns:

A Bindings that can be used to replace the state of this ScriptEngine.

getContext

ScriptContext getContext()

Returns the default ScriptContext of the ScriptEngine whose Bindings, Reader and Writers are used for script executions when no ScriptContext is specified.

Returns:

The default ScriptContext of the ScriptEngine.

setContext

void setContext(ScriptContext context)

Sets the default ScriptContext of the ScriptEngine whose Bindings, Reader and Writers are used for script executions when no ScriptContext is specified.

Parameters:

context - A ScriptContext that will replace the default ScriptContext in the ScriptEngine.

Throws:

NullPointerException - if context is null.

getFactory

ScriptEngineFactory getFactory()

Returns a ScriptEngineFactory for the class to which this ScriptEngine belongs.

Returns:

The ScriptEngineFactory