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1 /*
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2 Copyright (c) 2008 Franklin Schmidt <fschmidt@gmail.com>
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3
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4 Permission is hereby granted, free of charge, to any person obtaining a copy
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5 of this software and associated documentation files (the "Software"), to deal
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6 in the Software without restriction, including without limitation the rights
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7 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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8 copies of the Software, and to permit persons to whom the Software is
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9 furnished to do so, subject to the following conditions:
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10
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11 The above copyright notice and this permission notice shall be included in
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12 all copies or substantial portions of the Software.
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13
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14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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15 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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16 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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17 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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18 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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19 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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20 THE SOFTWARE.
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21 */
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22
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23 package fschmidt.db.util;
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24
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25 import java.lang.reflect.InvocationHandler;
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26 import java.lang.reflect.InvocationTargetException;
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27 import java.lang.reflect.Method;
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28 import java.lang.reflect.Proxy;
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29 import java.lang.reflect.Modifier;
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30 import java.util.Map;
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31 import java.util.HashMap;
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32 import java.util.Arrays;
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33
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34
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35 public class OverridingProxy<C,S> {
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36 private final Class<C> clsC;
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37 private final Map<MethodDesc,Method> methods = new HashMap<MethodDesc,Method>();
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38
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39 public OverridingProxy(Class<C> clsC,Class<S> clsS) {
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40 this.clsC = clsC;
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41 for( Method m : clsS.getDeclaredMethods() ) {
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42 if( Modifier.isPublic(m.getModifiers()) ) {
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43 m.setAccessible(true);
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44 methods.put( new MethodDesc(m), m );
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45 }
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46 }
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47 }
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48
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49 public C newInstance(C obj,S override) {
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50 @SuppressWarnings("unchecked")
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51 C c = (C)Proxy.newProxyInstance(
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52 clsC.getClassLoader(),
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53 new Class[]{clsC},
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54 newInvocationHandler(obj,override)
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55 );
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56 return c;
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57 }
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58
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59 protected InvocationHandler newInvocationHandler(C obj,S override) {
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60 return new OverridingInvocationHandler(obj,override);
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61 }
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62
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63 protected class OverridingInvocationHandler implements InvocationHandler {
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64 protected final C obj;
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65 protected final S override;
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66
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67 protected OverridingInvocationHandler(C obj,S override) {
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68 this.obj = obj;
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69 this.override = override;
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70 }
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71
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72 public Object invoke(Object proxy,Method method, Object[] args)
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73 throws Throwable
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74 {
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75 Method m2 = methods.get(new MethodDesc(method));
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76 try {
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77 return m2!=null ? m2.invoke(override,args) : method.invoke(obj,args);
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78 } catch (InvocationTargetException e) {
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79 throw e.getTargetException();
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80 }
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81 }
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82 }
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83
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84 private static final class MethodDesc {
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85 private final String name;
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86 private final Class[] params;
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87 private final Class rtn;
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88
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89 MethodDesc(Method method) {
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90 this.name = method.getName();
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91 this.params = method.getParameterTypes();
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92 this.rtn = method.getReturnType();
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93 }
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94
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95 public boolean equals(Object obj) {
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96 if( !(obj instanceof MethodDesc) )
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97 return false;
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98 MethodDesc md = (MethodDesc)obj;
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99 return name.equals(md.name) && Arrays.equals(params,md.params) && rtn.equals(md.rtn);
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100 }
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101
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102 public int hashCode() {
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103 return name.hashCode();
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104 }
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105
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106 public String toString() {
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107 StringBuilder buf = new StringBuilder();
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108 buf.append( rtn ).append( " " ).append( name ).append( "(" );
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109 if( params.length > 0 ) {
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110 buf.append( params[0] );
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111 for( int i=1; i<params.length; i++ ) {
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112 buf.append( ',' ).append( params[i] );
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113 }
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114 }
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115 buf.append( ")" );
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116 return buf.toString();
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117 }
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118 }
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119
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120 }
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