Interface IExpressionEvaluator
- All Superinterfaces:
ICookable
,IMultiCookable
- All Known Implementing Classes:
ExpressionEvaluator
,ExpressionEvaluator
The syntax of the expression to compile is that of a Java expression, as defined in JLS7, section 15. Notice that a Java expression does not have a concluding semicolon.
Example:
a + 7 * b
(Notice that this expression refers to two parameters "a" and "b", as explained below.)
The expression may optionally be preceeded with a sequence of import directives like
import java.text.*; new DecimalFormat("####,###.##").format(10200020.345345)
(Notice that the import directive is concluded with a semicolon, while the expression is not.) This feature is not available if you compile many expressions at a time (see below).
To set up an IExpressionEvaluator
object, proceed as follows:
- Create an
IExpressionEvaluator
-derived class - Configure the
IExpressionEvaluator
by calling any of the following methods: setExpressionType(Class)
setParameters(String[], Class[])
setThrownExceptions(Class[])
setParentClassLoader(ClassLoader)
setDefaultImports(String[])
-
Call any of the
ICookable.cook(String, java.io.Reader)
methods to scan, parse, compile and load the expression into the JVM.
After the IExpressionEvaluator
object is set up, the expression can be evaluated as often with different
parameter values (see evaluate(Object[])
). This evaluation is very fast, compared to the compilation.
Less common methods exist that allow for the specification of the name of the generated class, the class it
extends, the interfaces it implements, the name of the method that executes the expression, the exceptions that
this method (i.e. the expression) is allowed to throw, and the ClassLoader
that is used to define the
generated class and to load classes referenced by the expression.
If you want to compile many expressions at the same time, you have the option to cook an array of
expressions in one IExpressionEvaluator
by using the following methods:
setMethodNames(String[])
setParameters(String[][], Class[][])
setExpressionTypes(Class[])
setStaticMethod(boolean[])
setThrownExceptions(Class[][])
IMultiCookable.cook(String[], Reader[])
evaluate(int, Object[])
Notice that these methods have array parameters in contrast to their one-expression brethren.
Notice that for functionally identical IExpressionEvaluator
s, Object.equals(java.lang.Object)
will return true
. E.g. "a+b" and "c + d" are functionally
identical if "a" and "c" have the same type, and so do "b" and "d".
'JLS7' refers to the Java Language Specification, Java SE 7 Edition.
-
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final Class<?>
Deprecated.static final String
The fully qualified name of the generated class, iff not reconfigured bysetClassName(String)
.static final Class<?>
The type of all expressions that were not reconfigured withsetExpressionTypes(Class[])
. -
Method Summary
Modifier and TypeMethodDescription<T> T
createFastEvaluator
(Reader reader, Class<? extends T> interfaceToImplement, String... parameterNames) <T> T
createFastEvaluator
(String expression, Class<? extends T> interfaceToImplement, String... parameterNames) If the parameter and return types of the expression are known at compile time, then a "fast" expression evaluator can be instantiated throughcreateFastEvaluator(String, Class, String[])
.Null
arguments is equivalent withnew Object[0]
.Evaluates the expression with concrete parameter values.Class<?>
getClazz()
Class<?>
String[]
getMethod
(int idx) Method[]
void
setClassName
(String className) void
setCompileErrorHandler
(ErrorHandler compileErrorHandler) Installs anErrorHandler
which is invoked during compilation on each error.void
setDebuggingInformation
(boolean debugSource, boolean debugLines, boolean debugVars) Determines what kind of debugging information is included in the generates classes.void
setDefaultExpressionType
(Class<?> defaultExpressionType) Reconfigures the "default expression type"; if no expression type is configured for an expression, then, when cooking thisIExpressionEvaluator
, the "default expression type" is used for the expressionvoid
setDefaultImports
(String... defaultImports) void
setExpressionType
(Class<?> expressionType) Defines the type of the expression.void
setExpressionTypes
(Class<?>[] expressionTypes) Configures the types of the expressions.void
setExtendedClass
(Class<?> extendedType) void
setImplementedInterfaces
(Class<?>[] implementedTypes) Configures the interfaces that the generated class implements.void
setMethodName
(String methodName) void
setMethodNames
(String[] methodNames) void
setOverrideMethod
(boolean overrideMethod) void
setOverrideMethod
(boolean[] overrideMethod) void
setParameters
(String[][] parameterNames, Class<?>[][] parameterTypes) void
setParameters
(String[] parameterNames, Class<?>[] parameterTypes) void
setParentClassLoader
(ClassLoader parentClassLoader) The "parent class loader" is used to load referenced classes.void
setReturnType
(Class<?> returnType) Deprecated.UsesetExpressionType(Class)
insteadvoid
setStaticMethod
(boolean staticMethod) void
setStaticMethod
(boolean[] staticMethod) void
setThrownExceptions
(Class<?>[] thrownExceptions) void
setThrownExceptions
(Class<?>[][] thrownExceptions) void
setWarningHandler
(WarningHandler warningHandler) By default, warnings are discarded, but an application my install a customWarningHandler
.
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Field Details
-
DEFAULT_CLASS_NAME
The fully qualified name of the generated class, iff not reconfigured bysetClassName(String)
.- See Also:
-
DEFAULT_EXPRESSION_TYPE
The type of all expressions that were not reconfigured withsetExpressionTypes(Class[])
. -
ANY_TYPE
Deprecated.Since autoboxing was introduced in JANINO, this feature is no longer necessary because you can use expression typeObject
.class
Special value forsetExpressionType(Class)
that indicates that the expression may have any type.
-
-
Method Details
-
setParentClassLoader
The "parent class loader" is used to load referenced classes. Useful values are:System.getSystemClassLoader()
The running JVM's class path Thread.currentThread().getContextClassLoader()
ornull
The class loader effective for the invoking thread ClassLoaders.BOOTCLASSPATH_CLASS_LOADER
The running JVM's boot class path The parent class loader defaults to the current thread's context class loader.
-
setDebuggingInformation
void setDebuggingInformation(boolean debugSource, boolean debugLines, boolean debugVars) Determines what kind of debugging information is included in the generates classes. The default is typically "-g:none
". -
setCompileErrorHandler
Installs anErrorHandler
which is invoked during compilation on each error. (By default, the compilation throws aCompileException
on the first error and terminates.)If the given
ErrorHandler
throws aCompileException
, then the compilation terminates and the exception is propagated.If the given
ErrorHandler
does not throw aCompileException
but completes normally, then the compilation may or may not continue, depending on the error. Iff the compilation completes normally but errors were reported, then it will throw aCompileException
indicating the number of errors.In other words: The
ErrorHandler
may throw aCompileException
or not, but the compilation will definitely throw aCompileException
if one or more compile errors have occurred.- Parameters:
compileErrorHandler
-null
to restore the default behavior (throwing aCompileException
)
-
setWarningHandler
By default, warnings are discarded, but an application my install a customWarningHandler
.- Parameters:
warningHandler
-null
to indicate that no warnings be issued
-
evaluate
Evaluates the expression with concrete parameter values.Each argument value must have the same type as specified through the "parameterTypes" parameter of
setParameters(String[], Class[])
.Arguments of primitive type must passed with their wrapper class objects.
The object returned has the class as specified through
setExpressionType(Class)
.This method is thread-safe.
Null
arguments is equivalent withnew Object[0]
.- Parameters:
arguments
- The actual parameter values- Throws:
InvocationTargetException
-
setDefaultExpressionType
Reconfigures the "default expression type"; if no expression type is configured for an expression, then, when cooking thisIExpressionEvaluator
, the "default expression type" is used for the expression -
getDefaultExpressionType
Class<?> getDefaultExpressionType()- Returns:
- The currently configured "default expression type"
- See Also:
-
setImplementedInterfaces
Configures the interfaces that the generated class implements. -
setReturnType
Deprecated.UsesetExpressionType(Class)
instead -
setExpressionType
Defines the type of the expression.Defaults to
Object
.class
, which, thanks to autoboxing, allows for any expression type (including primitive types).If
expressionType
isvoid.class
, then the expression must be an invocation of avoid
method. -
setExpressionTypes
Configures the types of the expressions.Unless this method is called, all expressions have type
Object
.class
.If any expression has type
void.class
, then it must be an invocation of avoid
method. -
setOverrideMethod
void setOverrideMethod(boolean overrideMethod) -
setOverrideMethod
void setOverrideMethod(boolean[] overrideMethod) -
setParameters
-
setParameters
-
setClassName
- See Also:
-
setExtendedClass
-
setDefaultImports
-
getDefaultImports
String[] getDefaultImports()- See Also:
-
setStaticMethod
void setStaticMethod(boolean staticMethod) -
setStaticMethod
void setStaticMethod(boolean[] staticMethod) -
setMethodName
- See Also:
-
setMethodNames
-
setThrownExceptions
-
setThrownExceptions
-
evaluate
Null
arguments is equivalent withnew Object[0]
.- Throws:
InvocationTargetException
-
createFastEvaluator
<T> T createFastEvaluator(String expression, Class<? extends T> interfaceToImplement, String... parameterNames) throws CompileException If the parameter and return types of the expression are known at compile time, then a "fast" expression evaluator can be instantiated throughcreateFastEvaluator(String, Class, String[])
. Expression evaluation is faster than throughevaluate(Object[])
, because it is not done through reflection but through direct method invocation.Example:
public interface Foo { int bar(int a, int b); } ... ExpressionEvaluator ee = CompilerFactoryFactory.getDefaultCompilerFactory().newExpressionEvaluator(); // Optionally configure the EE here... ee.
setClassName
("Bar"); ee.setDefaultImports
(new String[] { "java.util.*" }); ee.setExtendedClass
(SomeOtherClass.class); ee.setParentClassLoader
(someClassLoader); // Optionally configure the EE here... Foo f = (Foo) ee.createFastEvaluator( "a + b", // expression to evaluate Foo.class, // interface that describes the expression's signature new String[] { "a", "b" } // the parameters' names ); System.out.println("1 + 2 = " + f.bar(1, 2)); // Evaluate the expressionAll other configuration (implemented type, static method, return type, method name, parameter names and types, thrown exceptions) are predetermined by the interfaceToImplement.
Notice: The
interfaceToImplement
must be accessible by the compiled class, i.e. either be declaredpublic
, or withprotected
or default access in the package of the compiled class (seesetClassName(String)
.- Throws:
CompileException
-
createFastEvaluator
<T> T createFastEvaluator(Reader reader, Class<? extends T> interfaceToImplement, String... parameterNames) throws CompileException, IOException - Throws:
CompileException
IOException
- See Also:
-
getMethod
Method getMethod()- See Also:
-
getMethod
- See Also:
-
getClazz
Class<?> getClazz()- See Also:
-
getResult
Method[] getResult()- See Also:
-
Object
.class