| Clover coverage report - PLT Utilities Test Coverage (plt-20120304-r5436) |
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| Source file | Conditionals | Statements | Methods | TOTAL | |||||||||||||||
| PreemptingClassLoader.java | 75% | 88.5% | 100% | 85.7% |
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| 1 | /*BEGIN_COPYRIGHT_BLOCK* | |
| 2 | ||
| 3 | PLT Utilities BSD License | |
| 4 | ||
| 5 | Copyright (c) 2007-2010 JavaPLT group at Rice University | |
| 6 | All rights reserved. | |
| 7 | ||
| 8 | Developed by: Java Programming Languages Team | |
| 9 | Rice University | |
| 10 | http://www.cs.rice.edu/~javaplt/ | |
| 11 | ||
| 12 | Redistribution and use in source and binary forms, with or without modification, are permitted | |
| 13 | provided that the following conditions are met: | |
| 14 | ||
| 15 | - Redistributions of source code must retain the above copyright notice, this list of conditions | |
| 16 | and the following disclaimer. | |
| 17 | - Redistributions in binary form must reproduce the above copyright notice, this list of | |
| 18 | conditions and the following disclaimer in the documentation and/or other materials provided | |
| 19 | with the distribution. | |
| 20 | - Neither the name of the JavaPLT group, Rice University, nor the names of the library's | |
| 21 | contributors may be used to endorse or promote products derived from this software without | |
| 22 | specific prior written permission. | |
| 23 | ||
| 24 | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR | |
| 25 | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND | |
| 26 | FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS AND | |
| 27 | CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 28 | DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 29 | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER | |
| 30 | IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT | |
| 31 | OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 32 | ||
| 33 | *END_COPYRIGHT_BLOCK*/ | |
| 34 | ||
| 35 | package edu.rice.cs.plt.reflect; | |
| 36 | ||
| 37 | import java.io.InputStream; | |
| 38 | import java.io.IOException; | |
| 39 | ||
| 40 | import edu.rice.cs.plt.iter.IterUtil; | |
| 41 | import edu.rice.cs.plt.io.IOUtil; | |
| 42 | ||
| 43 | /** | |
| 44 | * <p>A class loader that claims a set of classes available in its parent as its own. This allows classes | |
| 45 | * that would otherwise be loaded by a grandparent or distant ancestor to be loaded in a context that | |
| 46 | * gives them access to all classes available to the parent. For example, if a library must be loaded | |
| 47 | * with a {@link PathClassLoader}, while an adapter for that library is available on the static class | |
| 48 | * path (without any custom class loading), loading the adapter directly will lead to errors — the | |
| 49 | * library will not be visible to it. When loaded instead by this class loader, the adapter can see both the | |
| 50 | * application classes and the library classes.</p> | |
| 51 | * | |
| 52 | * <p>The implementation is somewhat limited: the only way to access a class definition in an arbitrary class | |
| 53 | * loader without actually <em>defining</em> that class is to invoke {@link ClassLoader#getResource} with | |
| 54 | * the name of a {@code .class} file. To work correctly, then, all preempted classes must be available | |
| 55 | * as class files via {@code parent.getResource(classFileName)}. Most class loaders (especially those | |
| 56 | * that simply load class files from some repository) follow the convention that a class will be loaded | |
| 57 | * only if a resource with the appropriate class file name exists. But there is no guarantee that all | |
| 58 | * class loaders (such as those that generate class definitions on the fly) will follow this convention.</p> | |
| 59 | */ | |
| 60 | public class PreemptingClassLoader extends AbstractClassLoader { | |
| 61 | ||
| 62 | private Iterable<String> _prefixes; | |
| 63 | ||
| 64 | /** | |
| 65 | * @param parent The source of all classes and resources to be loaded | |
| 66 | * @param prefixes A set of class name prefixes for which all matching classes will be defined by | |
| 67 | * this loader rather than a parent. Each prefix must be a package or class name | |
| 68 | * (partial names, like {@code "java.lang.Stri"}, will not match the full class name). | |
| 69 | */ | |
| 70 | 5 | public PreemptingClassLoader(ClassLoader parent, String... prefixes) { |
| 71 | 5 | this(parent, IterUtil.asIterable(prefixes)); |
| 72 | } | |
| 73 | ||
| 74 | /** | |
| 75 | * @param parent The source of all classes and resources to be loaded | |
| 76 | * @param prefixes A set of class name prefixes for which all matching classes will be defined by | |
| 77 | * this loader rather than a parent. Each prefix must be a package or class name | |
| 78 | * (partial names, like {@code "java.lang.Stri"}, will not match the full class name). | |
| 79 | */ | |
| 80 | 5 | public PreemptingClassLoader(ClassLoader parent, Iterable<? extends String> prefixes) { |
| 81 | 5 | super(parent); |
| 82 | 5 | _prefixes = IterUtil.snapshot(prefixes); |
| 83 | } | |
| 84 | ||
| 85 | /** | |
| 86 | * Load a class by following the standard search strategy specified by | |
| 87 | * {@link ClassLoader#loadClass(String, boolean)}, with one exception: if the name matches the set | |
| 88 | * of prefixes to preemptively load, the corresponding class file will be | |
| 89 | * loaded as a resource and defined here rather than allowing the parent to define the class. | |
| 90 | */ | |
| 91 | 23 | protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException { |
| 92 | 12 | if (!shouldPreempt(name)) { return super.loadClass(name, resolve); } |
| 93 | else { | |
| 94 | 11 | Class<?> result = findLoadedClass(name); // check if already loaded |
| 95 | 11 | if (result == null) { |
| 96 | 6 | String filename = name.replace('.', '/') + ".class"; |
| 97 | 6 | InputStream in = IOUtil.asBuffered(getResourceAsStream(filename)); |
| 98 | 0 | if (in == null) { throw new ClassNotFoundException("Resource not found: " + filename); } |
| 99 | 6 | try { |
| 100 | 6 | byte[] data = IOUtil.toByteArray(in); |
| 101 | ||
| 102 | // define package | |
| 103 | 6 | definePackageForClass(name); |
| 104 | ||
| 105 | 6 | result = defineClass(name, data, 0, data.length); |
| 106 | } | |
| 107 | catch (IOException e) { | |
| 108 | 0 | throw new ClassNotFoundException("Error in reading " + filename, e); |
| 109 | } | |
| 110 | finally { | |
| 111 | 6 | try { in.close(); } |
| 112 | catch (IOException e) { /* ignore */ } | |
| 113 | } | |
| 114 | } | |
| 115 | // if no exceptions have occurred, result is no longer null | |
| 116 | 0 | if (resolve) { resolveClass(result); } |
| 117 | 11 | return result; |
| 118 | } | |
| 119 | } | |
| 120 | ||
| 121 | 23 | private boolean shouldPreempt(String name) { |
| 122 | // TODO: improve efficiency by using a sorted data structure | |
| 123 | 23 | for (String p : _prefixes) { |
| 124 | 23 | if (name.startsWith(p)) { |
| 125 | 11 | if (name.equals(p) || name.startsWith(p + ".") || name.startsWith(p + "$")) { |
| 126 | 11 | return true; |
| 127 | } | |
| 128 | } | |
| 129 | } | |
| 130 | 12 | return false; |
| 131 | } | |
| 132 | } |
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