001 // Copyright 2004, 2005 The Apache Software Foundation 002 // 003 // Licensed under the Apache License, Version 2.0 (the "License"); 004 // you may not use this file except in compliance with the License. 005 // You may obtain a copy of the License at 006 // 007 // http://www.apache.org/licenses/LICENSE-2.0 008 // 009 // Unless required by applicable law or agreed to in writing, software 010 // distributed under the License is distributed on an "AS IS" BASIS, 011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012 // See the License for the specific language governing permissions and 013 // limitations under the License. 014 015 package org.apache.hivemind.service; 016 017 /** 018 * Used when fabricating a new class. Represents a wrapper around 019 * the Javassist library. 020 * 021 * <p> 022 * The core concept of Javassist is how method bodies (as well as constructor bodies, etc.) 023 * are specified ... as a very Java-like scripting language. The 024 * {@link org.apache.hivemind.service.BodyBuilder} class is <em>very</em> useful for assembling 025 * this method bodies. Details are available at the 026 * <a href="http://jboss.org/products/javassist">Javassist home page</a>. 027 * 028 * <p> 029 * Method bodies look largely like Java. References to java classes must be fully qualified. 030 * Several special variables are used: 031 * <ul> 032 * <li><code>$0</code> first parameter, equivalent to <code>this</code> in Java code (and can't 033 * be used when creating a static method) 034 * <li><code>$1, $2, ...</code> actual parameters to the method 035 * <li><code>$args</code> all the parameters as an <code>Object[]</code> 036 * <li><code>$r</code> the return type of the method, typically used as <code>return ($r) ...</code>. 037 * <code>$r</code> is valid with method that return <code>void</code>. This also handles conversions 038 * between wrapper types and primitive types. 039 * <li><code>$w</code> conversion from primitive type to wrapper type, used as <code>($w) foo()</code> where 040 * <code>foo()</code> returns a primitive type and a wrapper type is needed 041 * <li> 042 * </ul> 043 * 044 * @author Howard Lewis Ship 045 */ 046 public interface ClassFab 047 { 048 /** 049 * Adds the specified interface as an interface implemented by this class. 050 */ 051 public void addInterface(Class interfaceClass); 052 053 /** 054 * Adds a new field with the given name and type. The field is 055 * added as a private field. 056 */ 057 058 public void addField(String name, Class type); 059 060 public boolean canConvert(Class inputClass); 061 062 /** 063 * Convenience method for checking whether the fabricated class already contains 064 * a method. 065 * @param signature the signature 066 * @return whether or not the fabricated class already contains the method 067 */ 068 public boolean containsMethod( MethodSignature signature ); 069 070 /** 071 * Adds a method. The method is a public instance method. 072 * @return a method fabricator, used to add catch handlers. 073 * @param modifiers Modifiers for the method (see {@link java.lang.reflect.Modifier}). 074 * @param signature defines the name, return type, parameters and exceptions thrown 075 * @param body The body of the method. 076 * @throws org.apache.hivemind.ApplicationRuntimeException if a method with that signature has already 077 * been added, or if there is a Javassist compilation error 078 */ 079 080 public MethodFab addMethod(int modifiers, MethodSignature signature, String body); 081 082 /** 083 * Returns a previous defined method so that it can be further enhanced 084 * (perhaps by adding additional catches, etc.). 085 * 086 * @param signature the signature of the method previously added 087 * @return the MethodFab for that method, or null if the method has not been added yet 088 */ 089 090 public MethodFab getMethodFab(MethodSignature signature); 091 092 /** 093 * Adds a constructor to the class. The constructor will be public. 094 * @param parameterTypes the type of each parameter, or null if the constructor takes no parameters. 095 * @param exceptions the type of each exception, or null if the constructor throws no exceptions. 096 * @param body The body of the constructor. 097 */ 098 public void addConstructor(Class[] parameterTypes, Class[] exceptions, String body); 099 100 /** 101 * Invoked last to create the class. This will enforce that 102 * all abstract methods have been implemented in the (concrete) class. 103 */ 104 public Class createClass(); 105 }