Engine (Apache Commons JEXL 3.1 API)

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org.apache.commons.jexl3.internal
Class Engine

java.lang.Object
  org.apache.commons.jexl3.JexlEngine
      org.apache.commons.jexl3.internal.Engine

public class Engine
extends JexlEngine
extends JexlEngine

A JexlEngine implementation.

Since:: 2.0

Nested Class Summary
`protected static class`	`Engine.VarCollector` Utility class to collect variables.

Nested classes/interfaces inherited from class org.apache.commons.jexl3.JexlEngine
`JexlEngine.Options`

Field Summary
`protected JexlArithmetic`	`arithmetic` The `JexlArithmetic` instance.
`protected SoftCache<String,ASTJexlScript>`	`cache` The expression cache.
`protected int`	`cacheThreshold` The expression max length to hit the cache.
`protected boolean`	`cancellable` Whether expressions evaluated by this engine will throw JexlException.Cancel (true) or return null (false) when interrupted.
`protected Charset`	`charset` The default charset.
`protected boolean`	`debug` Whether error messages will carry debugging information.
`protected Map<String,Object>`	`functions` The map of 'prefix:function' to object implementing the namespaces.
`protected TemplateEngine`	`jxlt` The default jxlt engine.
`protected org.apache.commons.logging.Log`	`logger` The Log to which all JexlEngine messages will be logged.
`protected Parser`	`parser` The `Parser`; when parsing expressions, this engine uses the parser if it is not already in use otherwise it will create a new temporary one.
`protected AtomicBoolean`	`parsing` The atomic parsing flag; true whilst parsing.
`protected boolean`	`silent` Whether expressions evaluated by this engine will throw exceptions (false) or return null (true) on errors.
`protected boolean`	`strict` Whether this engine considers unknown variables, methods and constructors as errors.
`protected JexlUberspect`	`uberspect` The JexlUberspect instance.

Fields inherited from class org.apache.commons.jexl3.JexlEngine
`CONTEXT, EMPTY_CONTEXT, EMPTY_NS, TRY_FAILED`

Constructor Summary
`Engine()` Creates an engine with default arguments.
`Engine(JexlBuilder conf)` Creates a JEXL engine using the provided `JexlBuilder`.

Method Summary

void clearCache()
Clears the expression cache.

Script createExpression(JexlInfo info, String expression)
Creates an JexlExpression from a String containing valid JEXL syntax.

protected Interpreter createInterpreter(JexlContext context, Scope.Frame frame)
Creates an interpreter.

TemplateEngine createJxltEngine(boolean noScript, int cacheSize, char immediate, char deferred)
Creates a new instance of JxltEngine using this engine.

Script createScript(JexlInfo info, String scriptText, String[] names)
Creates a JexlScript from a String containing valid JEXL syntax.

protected Object doCreateInstance(Object clazz, Object... args)
Creates a new instance of an object using the most appropriate constructor based on the arguments.

JexlArithmetic getArithmetic()
Gets this engine underlying JexlArithmetic.

Charset getCharset()
Gets the charset used for parsing.

protected String[] getLocalVariables(JexlScript script)
Gets the array of local variable from a script.

protected String[] getParameters(JexlScript script)
Gets the array of parameters from a script.

Object getProperty(JexlContext context, Object bean, String expr)
Accesses properties of a bean using an expression.

Object getProperty(Object bean, String expr)
Accesses properties of a bean using an expression.

JexlUberspect getUberspect()
Gets this engine underlying JexlUberspect.

static Uberspect getUberspect(org.apache.commons.logging.Log logger, JexlUberspect.ResolverStrategy strategy)
Gets the default instance of Uberspect.

protected Set<List<String>> getVariables(ASTJexlScript script)
Gets the list of variables accessed by a script.

protected void getVariables(ASTJexlScript script, JexlNode node, Engine.VarCollector collector)
Fills up the list of variables accessed by a node.

Object invokeMethod(Object obj, String meth, Object... args)
Invokes an object's method by name and arguments.

boolean isCancellable()
Checks whether this engine will throw JexlException.Cancel (true) or return null (false) when interrupted during an execution.

boolean isDebug()
Checks whether this engine is in debug mode.

boolean isSilent()
Checks whether this engine throws JexlException during evaluation.

boolean isStrict()
Checks whether this engine considers unknown variables, methods, functions and constructors as errors.

protected TemplateEngine jxlt()
Gets and/or creates a default template engine.





<T> T

newInstance(Class<? extends T> clazz,
            Object... args)

Creates a new instance of an object using the most appropriate constructor based on the arguments.

Object newInstance(String clazz, Object... args)
Creates a new instance of an object using the most appropriate constructor based on the arguments.

protected ASTJexlScript parse(JexlInfo info, String src, Scope scope, boolean registers, boolean expression)
Parses an expression.

protected JexlContext.ThreadLocal putThreadLocal(JexlContext.ThreadLocal tls)
Swaps the current thread local context.

void setClassLoader(ClassLoader loader)
Sets the class loader used to discover classes in 'new' expressions.

void setProperty(JexlContext context, Object bean, String expr, Object value)
Assign properties of a bean using an expression.

void setProperty(Object bean, String expr, Object value)
Assign properties of a bean using an expression.

protected String trimSource(CharSequence str)
Trims the source from front and ending spaces.

Methods inherited from class org.apache.commons.jexl3.JexlEngine
`createExpression, createInfo, createInfo, createJxltEngine, createJxltEngine, createScript, createScript, createScript, createScript, createScript, createScript, createScript, createScript, getThreadContext, readSource, readSource, setThreadContext, toString`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

uberspect

protected final JexlUberspect uberspect

The JexlUberspect instance.

arithmetic

protected final JexlArithmetic arithmetic

The JexlArithmetic instance.

logger

protected final org.apache.commons.logging.Log logger

The Log to which all JexlEngine messages will be logged.

parsing

protected final AtomicBoolean parsing

The atomic parsing flag; true whilst parsing.

parser

protected final Parser parser

The Parser; when parsing expressions, this engine uses the parser if it is not already in use otherwise it will create a new temporary one.

strict

protected final boolean strict

Whether this engine considers unknown variables, methods and constructors as errors.

silent

protected final boolean silent

Whether expressions evaluated by this engine will throw exceptions (false) or return null (true) on errors. Default is false.

cancellable

protected final boolean cancellable

Whether expressions evaluated by this engine will throw JexlException.Cancel (true) or return null (false) when interrupted. Default is true when not silent and strict.

debug

protected final boolean debug

Whether error messages will carry debugging information.

functions

protected final Map<String,Object> functions

The map of 'prefix:function' to object implementing the namespaces.

cache

protected final SoftCache<String,ASTJexlScript> cache

The expression cache.

cacheThreshold

protected final int cacheThreshold

The expression max length to hit the cache.

charset

protected final Charset charset

The default charset.

jxlt

protected volatile TemplateEngine jxlt

The default jxlt engine.

Constructor Detail

Engine

public Engine()

Creates an engine with default arguments.

Engine

public Engine(JexlBuilder conf)

Creates a JEXL engine using the provided JexlBuilder.

Parameters:: conf - the builder

Method Detail

getUberspect

public static Uberspect getUberspect(org.apache.commons.logging.Log logger,
                                     JexlUberspect.ResolverStrategy strategy)

Gets the default instance of Uberspect.

This is lazily initialized to avoid building a default instance if there is no use for it. The main reason for not using the default Uberspect instance is to be able to use a (low level) introspector created with a given logger instead of the default one.

Parameters:: logger - the logger to use for the underlying Uberspect; strategy - the property resolver strategy
Returns:: Uberspect the default uberspector instance.

getUberspect

public JexlUberspect getUberspect()

Description copied from class: JexlEngine

Gets this engine underlying JexlUberspect.

Specified by:: getUberspect in class JexlEngine

Returns:: the uberspect

getArithmetic

public JexlArithmetic getArithmetic()

Description copied from class: JexlEngine

Gets this engine underlying JexlArithmetic.

Specified by:: getArithmetic in class JexlEngine

Returns:: the arithmetic

isDebug

public boolean isDebug()

Description copied from class: JexlEngine

Checks whether this engine is in debug mode.

Specified by:: isDebug in class JexlEngine

Returns:: true if debug is on, false otherwise

isSilent

public boolean isSilent()

Description copied from class: JexlEngine

Checks whether this engine throws JexlException during evaluation.

Specified by:: isSilent in class JexlEngine

Returns:: true if silent, false (default) otherwise

isStrict

public boolean isStrict()

Description copied from class: JexlEngine

Checks whether this engine considers unknown variables, methods, functions and constructors as errors.

Specified by:: isStrict in class JexlEngine

Returns:: true if strict, false otherwise

isCancellable

public boolean isCancellable()

Description copied from class: JexlEngine

Checks whether this engine will throw JexlException.Cancel (true) or return null (false) when interrupted during an execution.

Specified by:: isCancellable in class JexlEngine

Returns:: true if cancellable, false otherwise

setClassLoader

public void setClassLoader(ClassLoader loader)

Description copied from class: JexlEngine

Sets the class loader used to discover classes in 'new' expressions.

This method is not thread safe; it should be called as an optional step of the JexlEngine initialization code before expression creation & evaluation.

Specified by:: setClassLoader in class JexlEngine

Parameters:: loader - the class loader to use

getCharset

public Charset getCharset()

Description copied from class: JexlEngine

Gets the charset used for parsing.

Specified by:: getCharset in class JexlEngine

Returns:: the charset

createJxltEngine

public TemplateEngine createJxltEngine(boolean noScript,
                                       int cacheSize,
                                       char immediate,
                                       char deferred)

Description copied from class: JexlEngine

Creates a new instance of JxltEngine using this engine.

Specified by:: createJxltEngine in class JexlEngine

Parameters:: noScript - whether the JxltEngine only allows JEXL expressions or scripts; cacheSize - the number of expressions in this cache, default is 256; immediate - the immediate template expression character, default is '$'; deferred - the deferred template expression character, default is '#'
Returns:: a JEXL Template engine

clearCache

public void clearCache()

Description copied from class: JexlEngine

Clears the expression cache.

Specified by:: clearCache in class JexlEngine

createInterpreter

protected Interpreter createInterpreter(JexlContext context,
                                        Scope.Frame frame)

Creates an interpreter.

Parameters:: context - a JexlContext; if null, the empty context is used instead.; frame - the interpreter frame
Returns:: an Interpreter

createScript

public Script createScript(JexlInfo info,
                           String scriptText,
                           String[] names)

Description copied from class: JexlEngine

Creates a JexlScript from a String containing valid JEXL syntax. This method parses the script and validates the syntax.

Specified by:: createScript in class JexlEngine

Parameters:: info - An info structure to carry debugging information if needed; scriptText - A string containing valid JEXL syntax; names - The script parameter names used during parsing; a corresponding array of arguments containing values should be used during evaluation
Returns:: A JexlScript which can be executed using a JexlContext

createExpression

public Script createExpression(JexlInfo info,
                               String expression)

Description copied from class: JexlEngine

Creates an JexlExpression from a String containing valid JEXL syntax. This method parses the expression which must contain either a reference or an expression.

Specified by:: createExpression in class JexlEngine

Parameters:: info - An info structure to carry debugging information if needed; expression - A String containing valid JEXL syntax
Returns:: An JexlExpression which can be evaluated using a JexlContext

getProperty

public Object getProperty(Object bean,
                          String expr)

Description copied from class: JexlEngine

Accesses properties of a bean using an expression.

jexl.get(myobject, "foo.bar"); should equate to myobject.getFoo().getBar(); (or myobject.getFoo().get("bar"))

If the JEXL engine is silent, errors will be logged through its logger as warning.

Specified by:: getProperty in class JexlEngine

Parameters:: bean - the bean to get properties from; expr - the property expression
Returns:: the value of the property

getProperty

public Object getProperty(JexlContext context,
                          Object bean,
                          String expr)

Description copied from class: JexlEngine

Accesses properties of a bean using an expression.

If the JEXL engine is silent, errors will be logged through its logger as warning.

Specified by:: getProperty in class JexlEngine

Parameters:: context - the evaluation context; bean - the bean to get properties from; expr - the property expression
Returns:: the value of the property

setProperty

public void setProperty(Object bean,
                        String expr,
                        Object value)

Description copied from class: JexlEngine

Assign properties of a bean using an expression.

jexl.set(myobject, "foo.bar", 10); should equate to myobject.getFoo().setBar(10); (or myobject.getFoo().put("bar", 10) )

If the JEXL engine is silent, errors will be logged through its logger as warning.

Specified by:: setProperty in class JexlEngine

Parameters:: bean - the bean to set properties in; expr - the property expression; value - the value of the property

setProperty

public void setProperty(JexlContext context,
                        Object bean,
                        String expr,
                        Object value)

Description copied from class: JexlEngine

Assign properties of a bean using an expression.

If the JEXL engine is silent, errors will be logged through its logger as warning.

Specified by:: setProperty in class JexlEngine

Parameters:: context - the evaluation context; bean - the bean to set properties in; expr - the property expression; value - the value of the property

invokeMethod

public Object invokeMethod(Object obj,
                           String meth,
                           Object... args)

Description copied from class: JexlEngine

Invokes an object's method by name and arguments.

Specified by:: invokeMethod in class JexlEngine

Parameters:: obj - the method's invoker object; meth - the method's name; args - the method's arguments
Returns:: the method returned value or null if it failed and engine is silent

newInstance

public <T> T newInstance(Class<? extends T> clazz,
                         Object... args)

Description copied from class: JexlEngine

Creates a new instance of an object using the most appropriate constructor based on the arguments.

Specified by:: newInstance in class JexlEngine

Type Parameters:: T - the type of object
Parameters:: clazz - the class to instantiate; args - the constructor arguments
Returns:: the created object instance or null on failure when silent

newInstance

public Object newInstance(String clazz,
                          Object... args)

Description copied from class: JexlEngine

Creates a new instance of an object using the most appropriate constructor based on the arguments.

Specified by:: newInstance in class JexlEngine

Parameters:: clazz - the name of the class to instantiate resolved through this engine's class loader; args - the constructor arguments
Returns:: the created object instance or null on failure when silent

doCreateInstance

protected Object doCreateInstance(Object clazz,
                                  Object... args)

Creates a new instance of an object using the most appropriate constructor based on the arguments.

Parameters:: clazz - the class to instantiate; args - the constructor arguments
Returns:: the created object instance or null on failure when silent

putThreadLocal

protected JexlContext.ThreadLocal putThreadLocal(JexlContext.ThreadLocal tls)

Swaps the current thread local context.

Parameters:: tls - the context or null
Returns:: the previous thread local context

getVariables

protected Set<List<String>> getVariables(ASTJexlScript script)

Gets the list of variables accessed by a script.

This method will visit all nodes of a script and extract all variables whether they are written in 'dot' or 'bracketed' notation. (a.b is equivalent to a['b']).

Parameters:: script - the script
Returns:: the set of variables, each as a list of strings (ant-ish variables use more than 1 string) or the empty set if no variables are used

getVariables

protected void getVariables(ASTJexlScript script,
                            JexlNode node,
                            Engine.VarCollector collector)

Fills up the list of variables accessed by a node.

Parameters:: script - the owning script; node - the node; collector - the variable collector

getParameters

protected String[] getParameters(JexlScript script)

Gets the array of parameters from a script.

Parameters:: script - the script
Returns:: the parameters which may be empty (but not null) if no parameters were defined
Since:: 3.0

getLocalVariables

protected String[] getLocalVariables(JexlScript script)

Gets the array of local variable from a script.

Parameters:: script - the script
Returns:: the local variables array which may be empty (but not null) if no local variables were defined
Since:: 3.0

parse

protected ASTJexlScript parse(JexlInfo info,
                              String src,
                              Scope scope,
                              boolean registers,
                              boolean expression)

Parses an expression.

Parameters:: info - information structure; src - the expression to parse; scope - the script frame; registers - whether the parser should allow the unnamed '#number' syntax for 'registers'; expression - whether the parser allows scripts or only expressions
Returns:: the parsed tree
Throws:: JexlException - if any error occurred during parsing

trimSource

protected String trimSource(CharSequence str)

Trims the source from front and ending spaces.

Parameters:: str - expression to clean
Returns:: trimmed expression ending in a semi-colon

jxlt

protected TemplateEngine jxlt()

Gets and/or creates a default template engine.

Returns:: a template engine

Overview

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SUMMARY: NESTED | FIELD | CONSTR | METHOD

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org.apache.commons.jexl3.internal Class Engine

uberspect

arithmetic

logger

parsing

parser

strict

silent

cancellable

debug

functions

cache

cacheThreshold

charset

jxlt

Engine

Engine

getUberspect

getUberspect

getArithmetic

isDebug

isSilent

isStrict

isCancellable

setClassLoader

getCharset

createJxltEngine

clearCache

createInterpreter

createScript

createExpression

getProperty

getProperty

setProperty

setProperty

invokeMethod

newInstance

newInstance

doCreateInstance

putThreadLocal

getVariables

getVariables

getParameters

getLocalVariables

parse

trimSource

jxlt

org.apache.commons.jexl3.internal
Class Engine