org.codehaus.janino

Class ExpressionEvaluator

java.lang.Object

org.codehaus.commons.compiler.Cookable

org.codehaus.janino.SimpleCompiler

org.codehaus.janino.ClassBodyEvaluator

org.codehaus.janino.ScriptEvaluator

org.codehaus.janino.ExpressionEvaluator

All Implemented Interfaces:

IClassBodyEvaluator, ICookable, IExpressionEvaluator, IScriptEvaluator, ISimpleCompiler

public class ExpressionEvaluator
extends ScriptEvaluator
implements IExpressionEvaluator

This IExpressionEvaluator is implemented by creating and compiling a temporary compilation unit defining one class with one static method with one RETURN statement.

A number of "convenience constructors" exist that execute the set-up steps described for IExpressionEvaluator instantly.

If the parameter and return types of the expression are known at compile time, then a "fast" expression evaluator can be instantiated through createFastExpressionEvaluator(String, Class, String[], ClassLoader). Expression evaluation is faster than through ScriptEvaluator.evaluate(Object[]), because it is not done through reflection but through direct method invocation.

Example:

 public interface Foo {
     int bar(int a, int b);
 }
 ...
 Foo f = (Foo) ExpressionEvaluator.createFastExpressionEvaluator(
     "a + b",                    // expression to evaluate
     Foo.class,                  // interface that describes the expression's signature
     new String[] { "a", "b" },  // the parameters' names
     (ClassLoader) null          // Use current thread's context class loader
 );
 System.out.println("1 + 2 = " + f.bar(1, 2)); // Evaluate the expression
 

Notice: The interfaceToImplement must either be declared public, or with package scope in the root package (i.e. "no" package).

On my system (Intel P4, 2 GHz, MS Windows XP, JDK 1.4.1), expression "x + 1" evaluates as follows:

	Server JVM	Client JVM
Normal EE	23.7 ns	64.0 ns
Fast EE	31.2 ns	42.2 ns

(How can it be that interface method invocation is slower than reflection for the server JVM?)

Field Summary

Fields inherited from class org.codehaus.janino.ScriptEvaluator

optionalMethodNames, optionalParameterNames, optionalParameterTypes, optionalReturnTypes, optionalStaticMethod, optionalThrownExceptions

Fields inherited from class org.codehaus.janino.ClassBodyEvaluator

className, ZERO_CLASSES

Fields inherited from class org.codehaus.janino.SimpleCompiler

debugLines, debugSource, debugVars

Fields inherited from interface org.codehaus.commons.compiler.IExpressionEvaluator

ANY_TYPE

Fields inherited from interface org.codehaus.commons.compiler.IClassBodyEvaluator

DEFAULT_CLASS_NAME

Fields inherited from interface org.codehaus.commons.compiler.ICookable

BOOT_CLASS_LOADER, SYSTEM_PROPERTY_SOURCE_DEBUGGING_DIR, SYSTEM_PROPERTY_SOURCE_DEBUGGING_ENABLE

Constructor Summary

Constructors

Constructor and Description
ExpressionEvaluator()
ExpressionEvaluator(Scanner scanner, String className, Class optionalExtendedType, Class[] implementedTypes, boolean staticMethod, Class expressionType, String methodName, String[] parameterNames, Class[] parameterTypes, Class[] thrownExceptions, ClassLoader optionalParentClassLoader) Equivalent to
ExpressionEvaluator(String expression, Class expressionType, String[] parameterNames, Class[] parameterTypes) Equivalent to
ExpressionEvaluator(String expression, Class expressionType, String[] parameterNames, Class[] parameterTypes, Class[] thrownExceptions, Class optionalExtendedType, Class[] implementedTypes, ClassLoader optionalParentClassLoader) Equivalent to
ExpressionEvaluator(String expression, Class expressionType, String[] parameterNames, Class[] parameterTypes, Class[] thrownExceptions, ClassLoader optionalParentClassLoader) Equivalent to

Method Summary

Methods

Modifier and Type	Method and Description
static Object	createFastExpressionEvaluator(Scanner scanner, String[] optionalDefaultImports, String className, Class optionalExtendedType, Class interfaceToImplement, String[] parameterNames, ClassLoader optionalParentClassLoader) Deprecated.
static Object	createFastExpressionEvaluator(Scanner scanner, String className, Class optionalExtendedType, Class interfaceToImplement, String[] parameterNames, ClassLoader optionalParentClassLoader) Deprecated.
static Object	createFastExpressionEvaluator(String expression, Class interfaceToImplement, String[] parameterNames, ClassLoader optionalParentClassLoader) Deprecated.
protected Class	getDefaultReturnType()
static String[]	guessParameterNames(Scanner scanner) Guess the names of the parameters used in the given expression.
protected List	makeStatements(int idx, Scanner scanner) Fill the given block by parsing statements until EOF and adding them to the block.
void	setExpressionType(Class expressionType) Define the type of the expression.
void	setExpressionTypes(Class[] expressionTypes)

Methods inherited from class org.codehaus.janino.ScriptEvaluator

compileToMethods, cook, cook, cook, cook, cook, cook, createFastEvaluator, createFastEvaluator, createFastEvaluator, createFastScriptEvaluator, createFastScriptEvaluator, createFastScriptEvaluator, createFastScriptEvaluator, createInstance, evaluate, evaluate, getMethod, getMethod, makeMethodDeclaration, setMethodName, setMethodNames, setParameters, setParameters, setReturnType, setReturnTypes, setStaticMethod, setStaticMethod, setThrownExceptions, setThrownExceptions

Methods inherited from class org.codehaus.janino.ClassBodyEvaluator

addPackageMemberClassDeclaration, compileToClass, createFastClassBodyEvaluator, createFastClassBodyEvaluator, getClazz, makeCompilationUnit, setClassName, setDefaultImports, setExtendedClass, setExtendedType, setImplementedInterfaces, setImplementedTypes

Methods inherited from class org.codehaus.janino.SimpleCompiler

assertNotCooked, classesToTypes, classToType, compileToClassLoader, cook, cook, equals, getClassLoader, hashCode, main, setDebuggingInformation, setParentClassLoader, setParentClassLoader, setUpClassLoaders

Methods inherited from class org.codehaus.commons.compiler.Cookable

cook, cook, cook, cook, cook, cook, cook, cookFile, cookFile, cookFile, cookFile, readString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.codehaus.commons.compiler.IExpressionEvaluator

createFastEvaluator, createFastEvaluator, evaluate

Methods inherited from interface org.codehaus.commons.compiler.IScriptEvaluator

cook, cook, cook, cook, evaluate, getMethod, getMethod, setMethodName, setMethodNames, setParameters, setParameters, setReturnType, setReturnTypes, setStaticMethod, setStaticMethod, setThrownExceptions, setThrownExceptions

Methods inherited from interface org.codehaus.commons.compiler.IClassBodyEvaluator

createInstance, getClazz, setClassName, setDefaultImports, setExtendedClass, setExtendedType, setImplementedInterfaces, setImplementedTypes

Methods inherited from interface org.codehaus.commons.compiler.ICookable

cook, cook, cook, cook, cook, cook, cook, cook, cookFile, cookFile, cookFile, cookFile, setDebuggingInformation, setParentClassLoader

Constructor Detail

ExpressionEvaluator

public ExpressionEvaluator(String expression,
                   Class expressionType,
                   String[] parameterNames,
                   Class[] parameterTypes)
                    throws CompileException

Equivalent to

 ExpressionEvaluator ee = new ExpressionEvaluator();
 ee.setExpressionType(expressionType);
 ee.setParameters(parameterNames, parameterTypes);
 ee.cook(expression);

Throws:

CompileException

See Also:

ExpressionEvaluator(), setExpressionType(Class), ScriptEvaluator.setParameters(String[], Class[]), Cookable.cook(String)

ExpressionEvaluator

public ExpressionEvaluator(String expression,
                   Class expressionType,
                   String[] parameterNames,
                   Class[] parameterTypes,
                   Class[] thrownExceptions,
                   ClassLoader optionalParentClassLoader)
                    throws CompileException

Equivalent to

 ExpressionEvaluator ee = new ExpressionEvaluator();
 ee.setExpressionType(expressionType);
 ee.setParameters(parameterNames, parameterTypes);
 ee.setThrownExceptions(thrownExceptions);
 ee.setParentClassLoader(optionalParentClassLoader);
 ee.cook(expression);

Throws:

CompileException

See Also:

ExpressionEvaluator(), setExpressionType(Class), ScriptEvaluator.setParameters(String[], Class[]), ScriptEvaluator.setThrownExceptions(Class[]), SimpleCompiler.setParentClassLoader(ClassLoader), Cookable.cook(String)

ExpressionEvaluator

public ExpressionEvaluator(String expression,
                   Class expressionType,
                   String[] parameterNames,
                   Class[] parameterTypes,
                   Class[] thrownExceptions,
                   Class optionalExtendedType,
                   Class[] implementedTypes,
                   ClassLoader optionalParentClassLoader)
                    throws CompileException

Equivalent to

 ExpressionEvaluator ee = new ExpressionEvaluator();
 ee.setExpressionType(expressionType);
 ee.setParameters(parameterNames, parameterTypes);
 ee.setThrownExceptions(thrownExceptions);
 ee.setExtendedType(optionalExtendedType);
 ee.setImplementedTypes(implementedTypes);
 ee.setParentClassLoader(optionalParentClassLoader);
 ee.cook(expression);

Throws:

CompileException

See Also:

ExpressionEvaluator(), setExpressionType(Class), ScriptEvaluator.setParameters(String[], Class[]), ScriptEvaluator.setThrownExceptions(Class[]), ClassBodyEvaluator.setExtendedClass(Class), ClassBodyEvaluator.setImplementedInterfaces(Class[]), SimpleCompiler.setParentClassLoader(ClassLoader), Cookable.cook(String)

ExpressionEvaluator

public ExpressionEvaluator(Scanner scanner,
                   String className,
                   Class optionalExtendedType,
                   Class[] implementedTypes,
                   boolean staticMethod,
                   Class expressionType,
                   String methodName,
                   String[] parameterNames,
                   Class[] parameterTypes,
                   Class[] thrownExceptions,
                   ClassLoader optionalParentClassLoader)
                    throws CompileException,
                           IOException

Equivalent to

 ExpressionEvaluator ee = new ExpressionEvaluator();
 ee.setClassName(className);
 ee.setExtendedType(optionalExtendedType);
 ee.setImplementedTypes(implementedTypes);
 ee.setStaticMethod(staticMethod);
 ee.setExpressionType(expressionType);
 ee.setMethodName(methodName);
 ee.setParameters(parameterNames, parameterTypes);
 ee.setThrownExceptions(thrownExceptions);
 ee.setParentClassLoader(optionalParentClassLoader);
 ee.cook(scanner);

Throws:

CompileException

IOException

See Also:

IExpressionEvaluator, IClassBodyEvaluator.setClassName(String), IClassBodyEvaluator.setExtendedClass(Class), IClassBodyEvaluator.setImplementedInterfaces(Class[]), IScriptEvaluator.setStaticMethod(boolean), IExpressionEvaluator.setExpressionType(Class), IScriptEvaluator.setMethodName(String), IScriptEvaluator.setParameters(String[], Class[]), IScriptEvaluator.setThrownExceptions(Class[]), ICookable.setParentClassLoader(ClassLoader), ICookable.cook(Reader)

ExpressionEvaluator

public ExpressionEvaluator()

Method Detail

setExpressionType

public void setExpressionType(Class expressionType)

Description copied from interface: IExpressionEvaluator

Define the type of the expression. The special type IExpressionEvaluator.ANY_TYPE allows the expression to return any type (primitive or reference).

If expressionType is Void.TYPE, then the expression must be an invocation of a void method.

Defaults to IExpressionEvaluator.ANY_TYPE.

Specified by:

setExpressionType in interface IExpressionEvaluator

setExpressionTypes

public void setExpressionTypes(Class[] expressionTypes)

Specified by:

setExpressionTypes in interface IExpressionEvaluator

getDefaultReturnType

protected Class getDefaultReturnType()

Overrides:

getDefaultReturnType in class ScriptEvaluator

makeStatements

protected List makeStatements(int idx,
                  Scanner scanner)
                       throws CompileException,
                              IOException

Description copied from class: ScriptEvaluator

Fill the given block by parsing statements until EOF and adding them to the block.

Overrides:

makeStatements in class ScriptEvaluator

Throws:

CompileException

IOException

createFastExpressionEvaluator

public static Object createFastExpressionEvaluator(String expression,
                                   Class interfaceToImplement,
                                   String[] parameterNames,
                                   ClassLoader optionalParentClassLoader)
                                            throws CompileException

Deprecated.

Use ScriptEvaluator.createFastEvaluator(String, Class, String[]) instead:

 IExpressionEvaluator ee = CompilerFactoryFactory.getDefaultCompilerFactory().newExpressionEvaluator();
 ee.setParentClassLoader(optionalParentClassLoader);
 return ee.createFastEvaluator(expression, interfaceToImplement, parameterNames);
 

Throws:

CompileException

See Also:

ScriptEvaluator.createFastEvaluator(String, Class, String[])

createFastExpressionEvaluator

public static Object createFastExpressionEvaluator(Scanner scanner,
                                   String className,
                                   Class optionalExtendedType,
                                   Class interfaceToImplement,
                                   String[] parameterNames,
                                   ClassLoader optionalParentClassLoader)
                                            throws CompileException,
                                                   IOException

Deprecated.

Notice: This method is not declared in IExpressionEvaluator, and is hence only available in this implementation of org.codehaus.commons.compiler. To be independent from this particular implementation, try to switch to ScriptEvaluator.createFastEvaluator(Reader, Class, String[]).

Throws:

CompileException

IOException

See Also:

ScriptEvaluator.createFastEvaluator(Reader, Class, String[])

createFastExpressionEvaluator

public static Object createFastExpressionEvaluator(Scanner scanner,
                                   String[] optionalDefaultImports,
                                   String className,
                                   Class optionalExtendedType,
                                   Class interfaceToImplement,
                                   String[] parameterNames,
                                   ClassLoader optionalParentClassLoader)
                                            throws CompileException,
                                                   IOException

Deprecated.

Notice: This method is not declared in IExpressionEvaluator, and is hence only available in this implementation of org.codehaus.commons.compiler. To be independent from this particular implementation, try to switch to ScriptEvaluator.createFastEvaluator(Reader, Class, String[]).

Throws:

CompileException

IOException

See Also:

ScriptEvaluator.createFastEvaluator(Reader, Class, String[])

guessParameterNames

public static String[] guessParameterNames(Scanner scanner)
                                    throws CompileException,
                                           IOException

Guess the names of the parameters used in the given expression. The strategy is to look at all "ambiguous names" in the expression (e.g. in "a.b.c.d()", the ambiguous name is "a.b.c"), and then at the first components of the ambiguous name.

• If any component starts with an upper-case letter, then ambiguous name is assumed to be a type name.
• Otherwise, it is assumed to be a parameter name.

Throws:

CompileException

IOException

See Also:

Scanner.Scanner(String, Reader)