Engine (Apache Commons JEXL 3.0 API)

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

```
public class Engine
extends JexlEngine
```
A JexlEngine implementation.

Since:

2.0

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`protected class`	`Engine.SoftCache<K,V>` A soft referenced cache.
`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

Fields
Modifier and Type	Field and Description
`protected JexlArithmetic`	`arithmetic` The `JexlArithmetic` instance.
`protected Engine.SoftCache<String,ASTJexlScript>`	`cache` The expression cache.
`protected int`	`cacheThreshold` The expression max length to hit the cache.
`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 synchronizes on the parser.
`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

Constructors
Constructor and Description

Engine()
Creates an engine with default arguments.

Engine(JexlBuilder conf)
Creates a JEXL engine using the provided JexlBuilder.

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

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`clearCache()` Clears the expression cache.
`protected <K,V> Map<K,V>`	`createCache(int cacheSize)` Creates a 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`	`isDebug()` Checks whether this engine is in debug mode.
`boolean`	`isSilent()` Checks whether this engine throws JexlException during evaluation.
`boolean`	`isStrict()` Checks whether the 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.
  - parser
```
protected final Parser parser
```
    The Parser; when parsing expressions, this engine synchronizes on the parser.
  - 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.
  - 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 Engine.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 the engine considers unknown variables, methods, functions and constructors as errors.
    
    Specified by:
    
    isStrict in class JexlEngine
    
    Returns:
    true if strict, 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
  - 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
  - createCache
```
protected <K,V> Map<K,V> createCache(int cacheSize)
```
    Creates a cache.
    
    Type Parameters:
    K - the key type
    V - the value type
    Parameters:
    cacheSize - the cache size, must be > 0
    
    Returns:
    a Map usable as a cache bounded to the given size
  - 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
  - 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

Class Engine

Nested Class Summary

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

Field Summary

Fields inherited from class org.apache.commons.jexl3.JexlEngine

Constructor Summary

Method Summary

Methods inherited from class org.apache.commons.jexl3.JexlEngine

Methods inherited from class java.lang.Object

Field Detail

uberspect

arithmetic

logger

parser

strict

silent

debug

functions

cache

cacheThreshold

charset

jxlt

Constructor Detail

Engine

Engine

Method Detail

getUberspect

getUberspect

getArithmetic

isDebug

isSilent

isStrict

setClassLoader

getCharset

createJxltEngine

putThreadLocal

createCache

clearCache

createInterpreter

createScript

createExpression

getProperty

getProperty

setProperty

setProperty

invokeMethod

newInstance

newInstance

doCreateInstance

getVariables

getVariables

getParameters

getLocalVariables

parse

trimSource

jxlt