IScriptEvaluator (commons-compiler 3.1.6 API)

All Superinterfaces:

ICookable, IMultiCookable
```
public interface IScriptEvaluator
extends ICookable, IMultiCookable
```
An engine that executes a script in JVM bytecode.
The syntax of the script to compile is a sequence of import declarations (not allowed if you compile many scripts at a time, see below) followed by a sequence of statements, as defined in the Java Language Specification, Java SE 7 Edition, sections 7.5 and 14.

An implementation may or may not implement the concept of "local methods", i.e. method declarations being freely intermixed with statements.

Example:
```
   import java.text.*;

   System.out.println("HELLO");
   System.out.println(new DecimalFormat("####,###.##").format(a));
 
```
(Notice that this expression refers to a parameter "a", as explained below.)

The script may complete abnormally, e.g. through a RETURN statement:
```
   if (a == null) {
       System.out.println("Oops!");
       return;
   }
 
```
Optionally, the script may be declared with a non-void return type. In this case, the last statement of the script must be a RETURN statement (or a THROW statement), and all RETURN statements in the script must return a value with the given type.

The script evaluator is implemented by creating and compiling a temporary compilation unit defining one class with one method the body of which consists of the statements of the script.

To set up a IScriptEvaluator object, proceed as follows:
1. Create an IScriptEvaluator-implementing class.
2. Configure the IScriptEvaluator by calling any of the following methods:
3. Call any of the Cookable.cook(Reader) methods to scan, parse, compile and load the script into the JVM.
After the IScriptEvaluator object is created, the script can be executed as often with different parameter values (see evaluate(Object[])). This execution 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 script, the exceptions that this method (i.e. the script) is allowed to throw, and the ClassLoader that is used to define the generated class and to load classes referenced by the script.

If you want to compile many scripts at the same time, you have the option to cook an array of scripts in one IScriptEvaluator by using the following methods:
Notice that these methods have array parameters in contrast to their one-script brethren.

Field Summary

Fields
Modifier and Type	Field and Description
`static String`	`DEFAULT_METHOD_NAME` The name of the generated method(s), if no custom method name is configured with `setMethodNames(String[])`.
`static Class<?>`	`DEFAULT_RETURN_TYPE` The return type for any script for which no return type is explicitly configured.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`cook(Reader... readers)` Same as `ICookable.cook(Reader)`, but for multiple scripts.
`void`	`cook(String[] strings)` Same as `ICookable.cook(String)`, but for multiple scripts.
`void`	`cook(String[] fileNames, Reader[] readers)` Same as `ICookable.cook(String, Reader)`, but cooks a set of scripts into one class.
`void`	`cook(String[] fileNames, String[] strings)` Same as `ICookable.cook(String, String)`, but for multiple scripts.
`<T> T`	`createFastEvaluator(Reader reader, Class<T> interfaceToImplement, String[] parameterNames)` If the parameter and return types of the expression are known at compile time, then a "fast" script evaluator can be instantiated through this method.
`<T> T`	`createFastEvaluator(String script, Class<T> interfaceToImplement, String[] parameterNames)`
`Object`	`evaluate(int idx, Object[] arguments)` Same as `evaluate(Object[])`, but for multiple scripts.
`Object`	`evaluate(Object[] arguments)` Calls the script with concrete parameter values.
`Class<?>`	`getClazz()`
`String[]`	`getDefaultImports()`
`Class<?>`	`getDefaultReturnType()`
`Method`	`getMethod()`
`Method`	`getMethod(int idx)` Same as `getMethod()`, but for multiple scripts.
`Method[]`	`getResult()`
`void`	`setClassName(String className)`
`void`	`setCompileErrorHandler(ErrorHandler compileErrorHandler)` By default, `CompileException`s are thrown on compile errors, but an application my install its own `ErrorHandler`.
`void`	`setDebuggingInformation(boolean debugSource, boolean debugLines, boolean debugVars)` Determines what kind of debugging information is included in the generates classes.
`void`	`setDefaultImports(String... defaultImports)`
`void`	`setDefaultReturnType(Class<?> defaultReturnType)` When this `IScriptEvaluator` is coooked, then the `defaultReturnType` applies to all scripts for which no explicit return type was configured.
`void`	`setExtendedClass(Class<?> extendedClass)`
`void`	`setImplementedInterfaces(Class<?>[] implementedInterfaces)`
`void`	`setMethodName(String methodName)` Defines the name of the generated method.
`void`	`setMethodNames(String[] methodNames)` Same as `setMethodName(String)`, but for multiple scripts.
`void`	`setOverrideMethod(boolean overrideMethod)` Defines whether the generated method overrides a methods declared in a supertype.
`void`	`setOverrideMethod(boolean[] overrideMethod)` Same as `setOverrideMethod(boolean)`, but for multiple scripts.
`void`	`setParameters(String[][] names, Class<?>[][] types)` Same as `setParameters(String[], Class[])`, but for multiple scripts.
`void`	`setParameters(String[] names, Class<?>[] types)` Defines the names and types of the parameters of the generated method.
`void`	`setParentClassLoader(ClassLoader parentClassLoader)` The "parent class loader" is used to load referenced classes.
`void`	`setReturnType(Class<?> returnType)` Defines the return type of the generated method.
`void`	`setReturnTypes(Class<?>[] returnTypes)` Configures the return types of the generated methods.
`void`	`setStaticMethod(boolean staticMethod)` Defines whether the generated method should be STATIC or not.
`void`	`setStaticMethod(boolean[] staticMethod)` Same as `setStaticMethod(boolean)`, but for multiple scripts.
`void`	`setThrownExceptions(Class<?>[] thrownExceptions)` Defines the exceptions that the generated method may throw.
`void`	`setThrownExceptions(Class<?>[][] thrownExceptions)` Same as `setThrownExceptions(Class[])`, but for multiple scripts.
`void`	`setWarningHandler(WarningHandler warningHandler)` By default, warnings are discarded, but an application my install a custom `WarningHandler`.

Methods inherited from interface org.codehaus.commons.compiler.ICookable
cook, cook, cook, cook, cook, cook, cook, cook, cookFile, cookFile, cookFile, cookFile, getBytecodes, setSourceVersion, setTargetVersion

Methods inherited from interface org.codehaus.commons.compiler.IMultiCookable
cook, cook, cook, cook, cookFiles, cookFiles, cookFiles, cookFiles

Field Detail
- DEFAULT_METHOD_NAME
```
static final String DEFAULT_METHOD_NAME
```
  The name of the generated method(s), if no custom method name is configured with setMethodNames(String[]).
  The '*' in this string is replaced with the method index, starting at 0.
  
  See Also:
  
  Constant Field Values
- DEFAULT_RETURN_TYPE
```
static final Class<?> DEFAULT_RETURN_TYPE
```
  The return type for any script for which no return type is explicitly configured.

Method Detail

setParentClassLoader

void setParentClassLoader(@Nullable
                          ClassLoader parentClassLoader)

The "parent class loader" is used to load referenced classes. Useful values are:

`System.getSystemClassLoader()`	The running JVM's class path
`Thread.currentThread().getContextClassLoader()` or `null`	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
```
void setCompileErrorHandler(@Nullable
                            ErrorHandler compileErrorHandler)
```
By default, CompileExceptions are thrown on compile errors, but an application my install its own ErrorHandler.
Be aware that a single problem during compilation often causes a bunch of compile errors, so a good ErrorHandler counts errors and throws a CompileException when a limit is reached.

If the given ErrorHandler throws CompileExceptions, then the compilation is terminated and the exception is propagated.

If the given ErrorHandler does not throw CompileExceptions, then the compiler may or may not continue compilation, but must eventually throw a CompileException.

In other words: The ErrorHandler may throw a CompileException or not, but the compiler must definitely throw a CompileException if one or more compile errors have occurred.

Parameters:

compileErrorHandler - null to restore the default behavior (throwing a CompileException

setWarningHandler
```
void setWarningHandler(@Nullable
                       WarningHandler warningHandler)
```
By default, warnings are discarded, but an application my install a custom WarningHandler.

Parameters:

warningHandler - null to indicate that no warnings be issued

setClassName
```
void setClassName(String className)
```
See Also:

IClassBodyEvaluator.setClassName(String)

setImplementedInterfaces
```
void setImplementedInterfaces(Class<?>[] implementedInterfaces)
```
See Also:

IClassBodyEvaluator.setImplementedInterfaces(Class[])

setExtendedClass
```
void setExtendedClass(Class<?> extendedClass)
```
See Also:

IClassBodyEvaluator.setExtendedClass(Class)

setDefaultReturnType
```
void setDefaultReturnType(Class<?> defaultReturnType)
```
When this IScriptEvaluator is coooked, then the defaultReturnType applies to all scripts for which no explicit return type was configured.
The initial default return type (if you want, the "default-default" return type) is void.class.

See Also:

setReturnType(Class), setReturnTypes(Class[])

getDefaultReturnType
```
Class<?> getDefaultReturnType()
```
Returns:

The default return type that was previously configured with setDefaultReturnType(Class), or DEFAULT_RETURN_TYPE

setOverrideMethod
```
void setOverrideMethod(boolean overrideMethod)
```
Defines whether the generated method overrides a methods declared in a supertype.

setStaticMethod
```
void setStaticMethod(boolean staticMethod)
```
Defines whether the generated method should be STATIC or not. Defaults to true.

setReturnType
```
void setReturnType(Class<?> returnType)
```
Defines the return type of the generated method. Value null means "use the default return type".

See Also:

setDefaultReturnType(Class)

setMethodName

void setMethodName(@Nullable
                   String methodName)

Defines the name of the generated method. null means use a reasonable "eval*".

setParameters
```
void setParameters(String[] names,
                   Class<?>[] types)
```
Defines the names and types of the parameters of the generated method.
names.length and types.length must be equal. This invariant may be checked immediately, or later when the script is cooked.

The parameters can be of primitive type, e.g. double.class.

The default is to have zero parameters.

setThrownExceptions
```
void setThrownExceptions(Class<?>[] thrownExceptions)
```
Defines the exceptions that the generated method may throw.

evaluate
```
@Nullable
Object evaluate(@Nullable
                           Object[] arguments)
                    throws InvocationTargetException
```
Calls the script with concrete parameter values.
Each argument 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 setReturnType(Class).

This method is thread-safe.

Parameters:

arguments - The actual parameter values

Throws:

IllegalStateException - This IScriptEvaluator is not yet cooked

InvocationTargetException

getMethod
```
Method getMethod()
```
Returns:

The generated and loaded Method

Throws:

IllegalStateException - This IScriptEvaluator is not yet cooked

setOverrideMethod
```
void setOverrideMethod(boolean[] overrideMethod)
```
Same as setOverrideMethod(boolean), but for multiple scripts.

setStaticMethod
```
void setStaticMethod(boolean[] staticMethod)
```
Same as setStaticMethod(boolean), but for multiple scripts.

setReturnTypes
```
void setReturnTypes(Class<?>[] returnTypes)
```
Configures the return types of the generated methods. If an element of the array is null, then use the "default return type" for that script.

Parameters:

returnTypes - The methods' return types; null elements mean "use the default return type"

See Also:

setDefaultReturnType(Class), getDefaultReturnType()

setMethodNames
```
void setMethodNames(String[] methodNames)
```
Same as setMethodName(String), but for multiple scripts.
Define the names of the generated methods. By default the methods have distinct and implementation-specific names.

If two scripts have the same name, then they must have different parameter types (see setParameters(String[][], Class[][])).

setParameters

void setParameters(String[][] names,
                   Class<?>[][] types)

Same as setParameters(String[], Class[]), but for multiple scripts.

setThrownExceptions
```
void setThrownExceptions(Class<?>[][] thrownExceptions)
```
Same as setThrownExceptions(Class[]), but for multiple scripts.

cook
```
void cook(Reader... readers)
   throws CompileException,
          IOException
```
Same as ICookable.cook(Reader), but for multiple scripts.

Specified by:

cook in interface IMultiCookable

Throws:

CompileException

IOException

cook
```
void cook(String[] fileNames,
          Reader[] readers)
   throws CompileException,
          IOException
```
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 fileNames parameter to distinguish between the individual token sources.
Iff the number of scanners is one, then that single script may contain leading IMPORT directives.
s

Specified by:

cook in interface IMultiCookable

Throws:

IllegalStateException - if any of the preceding set...() had an array size different from that of scanners

CompileException

IOException

cook
```
void cook(String[] strings)
   throws CompileException
```
Same as ICookable.cook(String), but for multiple scripts.

Specified by:

cook in interface IMultiCookable

Throws:

CompileException

cook
```
void cook(String[] fileNames,
          String[] strings)
   throws CompileException
```
Same as ICookable.cook(String, String), but for multiple scripts.

Specified by:

cook in interface IMultiCookable

Throws:

CompileException

evaluate

@Nullable
Object evaluate(int idx,
                           @Nullable
                           Object[] arguments)
                    throws InvocationTargetException

Same as evaluate(Object[]), but for multiple scripts.

Throws:: InvocationTargetException

getMethod
```
Method getMethod(int idx)
```
Same as getMethod(), but for multiple scripts.

createFastEvaluator

<T> T createFastEvaluator(String script,
                          Class<T> interfaceToImplement,
                          String[] parameterNames)
                   throws CompileException

Parameters:: script - Contains the sequence of script tokens
Throws:: CompileException
See Also:: createFastEvaluator(Reader, Class, String[])

createFastEvaluator
```
<T> T createFastEvaluator(Reader reader,
                          Class<T> interfaceToImplement,
                          String[] parameterNames)
                   throws CompileException,
                          IOException
```
If the parameter and return types of the expression are known at compile time, then a "fast" script evaluator can be instantiated through this method.
Script evaluation is faster than through evaluate(Object[]), because it is not done through reflection but through direct method invocation.

Example:
```
 public interface Foo {
     int bar(int a, int b);
 }
 ...
 IScriptEvaluator se = CompilerFactoryFactory.getDefaultCompilerFactory().newScriptEvaluator();

 // Optionally configure the SE her:
 se.setClassName("Bar");
 se.setDefaultImports(new String[] { "java.util.*" });
 se.setExtendedClass(SomeOtherClass.class);
 se.setParentClassLoader(someClassLoader);

 Foo f = (Foo) se.createFastScriptEvaluator(
     "return a - b;",
     Foo.class,
     new String[] { "a", "b" }
 );
 System.out.println("1 - 2 = " + f.bar(1, 2));
 
```
All 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 either be declared public, or with package scope in the same package as the generated class (see setClassName(String)).
s
Parameters:

reader - Produces the stream of script tokens

interfaceToImplement - Must declare exactly one method

parameterNames - The names of the parameters of that method

Returns:

An object that implements the given interface

Throws:

CompileException

IOException

setDefaultImports
```
void setDefaultImports(String... defaultImports)
```
See Also:

IClassBodyEvaluator.setDefaultImports(String...)

getDefaultImports
```
String[] getDefaultImports()
```
See Also:

IClassBodyEvaluator.getDefaultImports()

getClazz
```
Class<?> getClazz()
```
See Also:

IClassBodyEvaluator.getClazz()

getResult
```
Method[] getResult()
```
Returns:

The generated and loaded methods that implement the cooked scripts

Throws:

IllegalStateException - This IScriptEvaluator is not yet cooked

Interface IScriptEvaluator

Field Summary

Method Summary

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

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

Field Detail

DEFAULT_METHOD_NAME

DEFAULT_RETURN_TYPE

Method Detail

setParentClassLoader

setDebuggingInformation

setCompileErrorHandler

setWarningHandler

setClassName

setImplementedInterfaces

setExtendedClass

setDefaultReturnType

getDefaultReturnType

setOverrideMethod

setStaticMethod

setReturnType

setMethodName

setParameters

setThrownExceptions

evaluate

getMethod

setOverrideMethod

setStaticMethod

setReturnTypes

setMethodNames

setParameters

setThrownExceptions

cook

cook

cook

cook

evaluate

getMethod

createFastEvaluator

createFastEvaluator

setDefaultImports

getDefaultImports

getClazz

getResult