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diff src/fschmidt/db/util/OverridingProxy.java @ 68:00520880ad02
add fschmidt source
author | Franklin Schmidt <fschmidt@gmail.com> |
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date | Sun, 05 Oct 2025 17:24:15 -0600 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/fschmidt/db/util/OverridingProxy.java Sun Oct 05 17:24:15 2025 -0600 @@ -0,0 +1,120 @@ +/* +Copyright (c) 2008 Franklin Schmidt <fschmidt@gmail.com> + +Permission is hereby granted, free of charge, to any person obtaining a copy +of this software and associated documentation files (the "Software"), to deal +in the Software without restriction, including without limitation the rights +to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +copies of the Software, and to permit persons to whom the Software is +furnished to do so, subject to the following conditions: + +The above copyright notice and this permission notice shall be included in +all copies or substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN +THE SOFTWARE. +*/ + +package fschmidt.db.util; + +import java.lang.reflect.InvocationHandler; +import java.lang.reflect.InvocationTargetException; +import java.lang.reflect.Method; +import java.lang.reflect.Proxy; +import java.lang.reflect.Modifier; +import java.util.Map; +import java.util.HashMap; +import java.util.Arrays; + + +public class OverridingProxy<C,S> { + private final Class<C> clsC; + private final Map<MethodDesc,Method> methods = new HashMap<MethodDesc,Method>(); + + public OverridingProxy(Class<C> clsC,Class<S> clsS) { + this.clsC = clsC; + for( Method m : clsS.getDeclaredMethods() ) { + if( Modifier.isPublic(m.getModifiers()) ) { + m.setAccessible(true); + methods.put( new MethodDesc(m), m ); + } + } + } + + public C newInstance(C obj,S override) { + @SuppressWarnings("unchecked") + C c = (C)Proxy.newProxyInstance( + clsC.getClassLoader(), + new Class[]{clsC}, + newInvocationHandler(obj,override) + ); + return c; + } + + protected InvocationHandler newInvocationHandler(C obj,S override) { + return new OverridingInvocationHandler(obj,override); + } + + protected class OverridingInvocationHandler implements InvocationHandler { + protected final C obj; + protected final S override; + + protected OverridingInvocationHandler(C obj,S override) { + this.obj = obj; + this.override = override; + } + + public Object invoke(Object proxy,Method method, Object[] args) + throws Throwable + { + Method m2 = methods.get(new MethodDesc(method)); + try { + return m2!=null ? m2.invoke(override,args) : method.invoke(obj,args); + } catch (InvocationTargetException e) { + throw e.getTargetException(); + } + } + } + + private static final class MethodDesc { + private final String name; + private final Class[] params; + private final Class rtn; + + MethodDesc(Method method) { + this.name = method.getName(); + this.params = method.getParameterTypes(); + this.rtn = method.getReturnType(); + } + + public boolean equals(Object obj) { + if( !(obj instanceof MethodDesc) ) + return false; + MethodDesc md = (MethodDesc)obj; + return name.equals(md.name) && Arrays.equals(params,md.params) && rtn.equals(md.rtn); + } + + public int hashCode() { + return name.hashCode(); + } + + public String toString() { + StringBuilder buf = new StringBuilder(); + buf.append( rtn ).append( " " ).append( name ).append( "(" ); + if( params.length > 0 ) { + buf.append( params[0] ); + for( int i=1; i<params.length; i++ ) { + buf.append( ',' ).append( params[i] ); + } + } + buf.append( ")" ); + return buf.toString(); + } + } + +}