org.codehaus.commons.compiler.jdk
Class ExpressionEvaluator

java.lang.Object
  org.codehaus.commons.compiler.Cookable
      org.codehaus.commons.compiler.jdk.SimpleCompiler
          org.codehaus.commons.compiler.jdk.ClassBodyEvaluator
              org.codehaus.commons.compiler.jdk.ScriptEvaluator
                  org.codehaus.commons.compiler.jdk.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 ScriptEvaluator.createFastEvaluator(String, Class, String[]). 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.commons.compiler.jdk.ScriptEvaluator

optionalOverrideMethod, optionalStaticMethod

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

ExpressionEvaluator()

ExpressionEvaluator(String expression, Class<?> expressionType, String[] parameterNames, Class<?>[] parameterTypes)
Equivalent to ExpressionEvaluator ee = new ExpressionEvaluator(); ee.setExpressionType(expressionType); ee.setParameters(parameterNames, parameterTypes); ee.cook(expression);

ExpressionEvaluator(String expression, Class<?> expressionType, String[] parameterNames, Class<?>[] parameterTypes, Class<?>[] thrownExceptions, Class<?> optionalExtendedType, Class<?>[] implementedTypes, ClassLoader optionalParentClassLoader)
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);

ExpressionEvaluator(String expression, Class<?> expressionType, String[] parameterNames, Class<?>[] parameterTypes, Class<?>[] thrownExceptions, ClassLoader optionalParentClassLoader)
Equivalent to ExpressionEvaluator ee = new ExpressionEvaluator(); ee.setExpressionType(expressionType); ee.setParameters(parameterNames, parameterTypes); ee.setThrownExceptions(thrownExceptions); ee.setParentClassLoader(optionalParentClassLoader); ee.cook(expression);

Method Summary

void	cook(String[] optionalFileNames, Reader[] readers) Same as ICookable.cook(String, Reader), but cooks a set of scripts into one class.
protected Class<?>	getDefaultReturnType() The default return type of an expression is Object.
void	setExpressionType(Class expressionType) Define the type of the expression.
void	setExpressionTypes(Class[] expressionTypes) Same as IExpressionEvaluator.setExpressionType(Class), but for multiple expressions.
void	setReturnType(Class returnType) Deprecated.
void	setReturnTypes(Class[] returnTypes) Deprecated.

Methods inherited from class org.codehaus.commons.compiler.jdk.ScriptEvaluator

cook, cook, cook, cook, cook, createFastEvaluator, createFastEvaluator, createInstance, evaluate, evaluate, getMethod, getMethod, setMethodName, setMethodNames, setOverrideMethod, setOverrideMethod, setParameters, setParameters, setStaticMethod, setStaticMethod, setThrownExceptions, setThrownExceptions

Methods inherited from class org.codehaus.commons.compiler.jdk.ClassBodyEvaluator

cook, getClazz, parseImportDeclarations, setClassName, setDefaultImports, setExtendedClass, setExtendedType, setImplementedInterfaces, setImplementedTypes

Methods inherited from class org.codehaus.commons.compiler.jdk.SimpleCompiler

assertCooked, assertNotCooked, getClassLoader, setCompileErrorHandler, setDebuggingInformation, setParentClassLoader, setParentClassLoader, setWarningHandler

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, equals, finalize, getClass, hashCode, 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, evaluate, getMethod, getMethod, setMethodName, setMethodNames, setOverrideMethod, setOverrideMethod, setParameters, setParameters, 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, setCompileErrorHandler, setDebuggingInformation, setParentClassLoader, setWarningHandler

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()

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)

Description copied from interface: IExpressionEvaluator

Same as IExpressionEvaluator.setExpressionType(Class), but for multiple expressions.

Specified by:

setExpressionTypes in interface IExpressionEvaluator

setReturnType

@Deprecated
public final void setReturnType(Class returnType)

Deprecated.

Description copied from interface: IScriptEvaluator

Defines the return type of the generated method. The meaning of a null value is implementation-dependent.

Specified by:

setReturnType in interface IExpressionEvaluator

Specified by:

setReturnType in interface IScriptEvaluator

Overrides:

setReturnType in class ScriptEvaluator

setReturnTypes

@Deprecated
public final void setReturnTypes(Class[] returnTypes)

Deprecated.

Description copied from interface: IScriptEvaluator

Defines the return types of the generated methods. The meaning of null elements is implementation-dependent.

Specified by:

setReturnTypes in interface IExpressionEvaluator

Specified by:

setReturnTypes in interface IScriptEvaluator

Overrides:

setReturnTypes in class ScriptEvaluator

getDefaultReturnType

protected Class<?> getDefaultReturnType()

The default return type of an expression is Object.

Overrides:

getDefaultReturnType in class ScriptEvaluator

cook

public void cook(String[] optionalFileNames,
                 Reader[] readers)
          throws CompileException,
                 IOException

Description copied from interface: IScriptEvaluator

Same as ICookable.cook(String, Reader), but cooks a set of scripts into one class. Notice that if any of the scripts causes trouble, the entire compilation will fail. If you need to report which of the scripts causes the exception, you may want to use the optionalFileNames parameter to distinguish between the individual token sources.

If and only if the number of scanners is one, then that single script may contain leading IMPORT directives.

Specified by:

cook in interface IScriptEvaluator

Overrides:

cook in class ScriptEvaluator

Throws:

CompileException

IOException