org.apache.hivemind.service
Interface ClassFab

All Known Implementing Classes:

ClassFabImpl

public interface ClassFab

Used when fabricating a new class. Represents a wrapper around the Javassist library.

The core concept of Javassist is how method bodies (as well as constructor bodies, etc.) are specified ... as a very Java-like scripting language. The BodyBuilder class is very useful for assembling this method bodies. Details are available at the Javassist home page.

Method bodies look largely like Java. References to java classes must be fully qualified. Several special variables are used:

• $0 first parameter, equivalent to this in Java code (and can't be used when creating a static method)
• $1, $2, ... actual parameters to the method
• $args all the parameters as an Object[]
• $r the return type of the method, typically used as return ($r) .... $r is valid with method that return void. This also handles conversions between wrapper types and primitive types.
• $w conversion from primitive type to wrapper type, used as ($w) foo() where foo() returns a primitive type and a wrapper type is needed

Author:

Howard Lewis Ship

Method Summary

void	addConstructor(java.lang.Class[] parameterTypes, java.lang.Class[] exceptions, java.lang.String body) Adds a constructor to the class.
void	addField(java.lang.String name, java.lang.Class type) Adds a new field with the given name and type.
void	addInterface(java.lang.Class interfaceClass) Adds the specified interface as an interface implemented by this class.
MethodFab	addMethod(int modifiers, MethodSignature signature, java.lang.String body) Adds a method.
boolean	containsMethod(MethodSignature signature) Convenience method for checking whether the fabricated class already contains a method.
java.lang.Class	createClass() Invoked last to create the class.
MethodFab	getMethodFab(MethodSignature signature) Returns a previous defined method so that it can be further enhanced (perhaps by adding additional catches, etc.).

Method Detail

addInterface

void addInterface(java.lang.Class interfaceClass)

Adds the specified interface as an interface implemented by this class.

addField

void addField(java.lang.String name,
              java.lang.Class type)

Adds a new field with the given name and type. The field is added as a private field.

containsMethod

boolean containsMethod(MethodSignature signature)

Convenience method for checking whether the fabricated class already contains a method.

Parameters:

signature - the signature

Returns:

whether or not the fabricated class already contains the method

addMethod

MethodFab addMethod(int modifiers,
                    MethodSignature signature,
                    java.lang.String body)

Adds a method. The method is a public instance method.

Parameters:

modifiers - Modifiers for the method (see Modifier).

signature - defines the name, return type, parameters and exceptions thrown

body - The body of the method.

Returns:

a method fabricator, used to add catch handlers.

Throws:

ApplicationRuntimeException - if a method with that signature has already been added, or if there is a Javassist compilation error

getMethodFab

MethodFab getMethodFab(MethodSignature signature)

Returns a previous defined method so that it can be further enhanced (perhaps by adding additional catches, etc.).

Parameters:

signature - the signature of the method previously added

Returns:

the MethodFab for that method, or null if the method has not been added yet

addConstructor

void addConstructor(java.lang.Class[] parameterTypes,
                    java.lang.Class[] exceptions,
                    java.lang.String body)

Adds a constructor to the class. The constructor will be public.

Parameters:

parameterTypes - the type of each parameter, or null if the constructor takes no parameters.

exceptions - the type of each exception, or null if the constructor throws no exceptions.

body - The body of the constructor.

createClass

java.lang.Class createClass()

Invoked last to create the class. This will enforce that all abstract methods have been implemented in the (concrete) class.