org.codehaus.commons.compiler

Interface IClassBodyEvaluator

All Superinterfaces:

ICookable

public interface IClassBodyEvaluator
extends ICookable

Parses a class body and returns it as a Class object ready for use with java.lang.reflect.

Example:

   import java.util.*;

   static private int a = 1;
   private int b = 2;

   public void func(int c, int d) {
       return func2(c, d);
   }

   private static void func2(int e, int f) {
       return e * f;
   }
 

To set up an IClassBodyEvaluator object, proceed as follows:

1. Create an IClassBodyEvaluator-implementing class.
2. Configure the IClassBodyEvaluator by calling any of the following methods:
• setDefaultImports(String[])
• setClassName(String)
• setExtendedClass(Class)
• setImplementedInterfaces(Class[])
• setParentClassLoader(ClassLoader)
3. Call any of the ICookable.cook(String, java.io.Reader) methods to scan, parse, compile and load the class body into the JVM.

To compile a class body and immediately instantiate an object, the createInstance(Reader) methods can be used.

The generated class may optionally extend/implement a given type; the returned instance can safely be type-cast to that baseType.

Example:

 public interface Foo {
     int bar(int a, int b);
 }
 ...
 IClassBodyEvaluator cbe = CompilerFactoryFactory.getDefaultCompilerFactory(). newClassBodyEvaluator();
 Foo f = (Foo) ClassBodyEvaluator.createFastClassBodyEvaluator(
     new Scanner(null, new StringReader("public int bar(int a, int b) { return a + b; }")),
     Foo.class,                  // Base type to extend/implement
     (ClassLoader) null          // Use current thread's context class loader
 );
 System.out.println("1 + 2 = " + f.bar(1, 2));
 

Field Summary

Fields

Modifier and Type	Field and Description
static String	DEFAULT_CLASS_NAME Default name for the generated class.

Method Summary

Modifier and Type	Method and Description
Object	createInstance(Reader reader) Scans, parses and compiles a class body from the tokens delivered by the the given Reader, then creates and returns an instance of that class.
Class<?>	getClazz()
String[]	getDefaultImports()
void	setClassName(String className) Sets the name of the generated class.
void	setCompileErrorHandler(ErrorHandler compileErrorHandler) Installs an ErrorHandler 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	setDefaultImports(String... defaultImports) "Default imports" add to the system import "java.lang", i.e. the evaluator may refer to classes imported by default imports without having to explicitly declare IMPORT statements.
void	setExtendedClass(Class<?> extendedClass) Sets a particular superclass that the generated class will extend.
void	setExtendedType(Class<?> extendedClass) Deprecated. Use setExtendedClass(Class) instead
void	setImplementedInterfaces(Class<?>[] implementedInterfaces) Sets a particular set of interfaces that the generated class will implement.
void	setImplementedTypes(Class<?>[] implementedInterfaces) Deprecated. Use setImplementedInterfaces(Class[]) instead
void	setParentClassLoader(ClassLoader parentClassLoader) The "parent class loader" is used to load referenced classes.
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

Field Detail

DEFAULT_CLASS_NAME

static final String DEFAULT_CLASS_NAME

Default name for the generated class.

See Also:

Constant Field Values

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)

Installs an ErrorHandler which is invoked during compilation on each error. (By default, the compilation throws a CompileException on the first error and terminates.)

If the given ErrorHandler throws a CompileException, then the compilation terminates and the exception is propagated.

If the given ErrorHandler does not throw a CompileException 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 a CompileException indicating the number of errors.

In other words: The ErrorHandler may throw a CompileException or not, but the compilation will 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

setDefaultImports

void setDefaultImports(String... defaultImports)

"Default imports" add to the system import "java.lang", i.e. the evaluator may refer to classes imported by default imports without having to explicitly declare IMPORT statements.

Notice that JDK 5 "static imports" are also supported, as shown here:

     sc.setDefaultImports(
         "java.util.Map",                          // Single type import
         "java.io.*",                              // Type-import-on-demand
         "static java.util.Collections.EMPTY_MAP", // Single static import
         "static java.util.Collections.*",         // Static-import-on-demand
     );

getDefaultImports

String[] getDefaultImports()

Returns:

The default imports that were previously configured with setDefaultImports(String...)

setClassName

void setClassName(String className)

Sets the name of the generated class. Defaults to DEFAULT_CLASS_NAME. In most cases, there is no need to set this name, because the generated class is loaded into its own ClassLoader where its name cannot collide with classes generated by other evaluators.

One reason to use this function is to have a class name in a non-default package, which can be relevant when types and members with DEFAULT accessibility are accessed.

setExtendedClass

void setExtendedClass(@Nullable
                      Class<?> extendedClass)

Sets a particular superclass that the generated class will extend. If extendedClass is null, the generated class will extend Object.

The usual reason to set a base class for an evaluator is that the generated class can directly access the superclass's (non-private) members.

setExtendedType

@Deprecated
void setExtendedType(@Nullable
                                  Class<?> extendedClass)

Deprecated. Use setExtendedClass(Class) instead

setImplementedInterfaces

void setImplementedInterfaces(Class<?>[] implementedInterfaces)

Sets a particular set of interfaces that the generated class will implement.

setImplementedTypes

@Deprecated
void setImplementedTypes(Class<?>[] implementedInterfaces)

Deprecated. Use setImplementedInterfaces(Class[]) instead

getClazz

Class<?> getClazz()

Returns:

The generated Class

Throws:

IllegalStateException - This IClassBodyEvaluator is not yet cooked

createInstance

Object createInstance(Reader reader)
               throws CompileException,
                      IOException

Scans, parses and compiles a class body from the tokens delivered by the the given Reader, then creates and returns an instance of that class.

Parameters:

reader - Source of class body tokens

Returns:

An object that extends the extendedType and implements the given implementedTypes

Throws:

CompileException

IOException