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1
16
17 package org.springframework.instrument.classloading;
18
19 import java.io.IOException  ;
20 import java.io.InputStream ;
21 import java.lang.instrument.ClassFileTransformer ;
22 import java.lang.instrument.IllegalClassFormatException ;
23 import java.net.URL ;
24 import java.util.ArrayList ;
25 import java.util.Enumeration ;
26 import java.util.HashMap ;
27 import java.util.LinkedList ;
28 import java.util.List ;
29 import java.util.Map ;
30
31 import org.springframework.util.Assert;
32 import org.springframework.util.FileCopyUtils;
33 import org.springframework.util.StringUtils;
34
35
47 public class ShadowingClassLoader extends ClassLoader {
48
49
50 public static final String [] DEFAULT_EXCLUDED_PACKAGES = new String [] {"java.", "javax.", "sun.", "com.sun.",
51 "org.w3c.", "org.xml.", "org.dom4j.", "org.aspectj.", "org.apache.xerces.", "org.apache.commons.logging."};
52
53
54
55 public final List <String > optionalExcludedPackages = new ArrayList <String >();
56
57 private final ClassLoader enclosingClassLoader;
58
59 private final List <ClassFileTransformer > classFileTransformers = new LinkedList <ClassFileTransformer >();
60
61 private final Map <String , Class > classCache = new HashMap <String , Class >();
62
63
64
68 public ShadowingClassLoader(ClassLoader enclosingClassLoader) {
69 Assert.notNull(enclosingClassLoader, "Enclosing ClassLoader must not be null");
70 this.enclosingClassLoader = enclosingClassLoader;
71 }
72
73
78 public void addTransformer(ClassFileTransformer transformer) {
79 Assert.notNull(transformer, "Transformer must not be null");
80 this.classFileTransformers.add(transformer);
81 }
82
83
88 public void copyTransformers(ShadowingClassLoader other) {
89 Assert.notNull(other, "Other ClassLoader must not be null");
90 this.classFileTransformers.addAll(other.classFileTransformers);
91 }
92
93
94 public Class <?> loadClass(String name) throws ClassNotFoundException {
95 if (shouldShadow(name)) {
96 Class cls = this.classCache.get(name);
97 if (cls != null) {
98 return cls;
99 }
100 return doLoadClass(name);
101 }
102 else {
103 return this.enclosingClassLoader.loadClass(name);
104 }
105 }
106
107
111 private boolean shouldShadow(String className) {
112 return (!className.equals(getClass().getName()) && !className.endsWith("ShadowingClassLoader")
113 && !isExcludedPackage(className) && !isClassNameExcludedFromShadowing(className));
114 }
115
116
120 private boolean isExcludedPackage(String className) {
121 for (int i = 0; i < DEFAULT_EXCLUDED_PACKAGES.length; i++) {
122 if (className.startsWith(DEFAULT_EXCLUDED_PACKAGES[i])) {
123 return true;
124 }
125 }
126 for (String pkg : this.optionalExcludedPackages) {
128 if (className.startsWith(pkg)) {
129 return true;
130 }
131 }
132 return false;
133 }
134
135
140 protected boolean isClassNameExcludedFromShadowing(String className) {
141 return false;
142 }
143
144 private Class doLoadClass(String name) throws ClassNotFoundException {
145 String internalName = StringUtils.replace(name, ".", "/") + ".class";
146 InputStream is = this.enclosingClassLoader.getResourceAsStream(internalName);
147 if (is == null) {
148 throw new ClassNotFoundException (name);
149 }
150 try {
151 byte[] bytes = FileCopyUtils.copyToByteArray(is);
152 bytes = applyTransformers(name, bytes);
153 Class cls = defineClass(name, bytes, 0, bytes.length);
154 this.classCache.put(name, cls);
155 return cls;
156 }
157 catch (IOException ex) {
158 throw new ClassNotFoundException ("Cannot load resource for class [" + name + "]", ex);
159 }
160 }
161
162 private byte[] applyTransformers(String name, byte[] bytes) {
163 String internalName = StringUtils.replace(name, ".", "/");
164 try {
165 for (ClassFileTransformer transformer : this.classFileTransformers) {
166 byte[] transformed = transformer.transform(this, internalName, null, null, bytes);
167 bytes = (transformed != null ? transformed : bytes);
168 }
169 return bytes;
170 }
171 catch (IllegalClassFormatException ex) {
172 throw new IllegalStateException (ex);
173 }
174 }
175
176 public URL getResource(String name) {
177 return this.enclosingClassLoader.getResource(name);
178 }
179
180 public InputStream getResourceAsStream(String name) {
181 return this.enclosingClassLoader.getResourceAsStream(name);
182 }
183
184 public Enumeration <URL > getResources(String name) throws IOException {
185 return this.enclosingClassLoader.getResources(name);
186 }
187
188
191 public List <String > getOptionalExcludedPackages() {
192 return this.optionalExcludedPackages;
193 }
194
195 }
196 |
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