1 /*

     2  * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 

    24 package com.oracle.java.testlibrary;

    25 

    26 import java.io.ByteArrayOutputStream;

    27 import java.io.IOException;

    28 import java.io.OutputStream;

    29 

    30 import java.net.URI;

    31 import java.util.Arrays;

    32 

    33 import javax.tools.ForwardingJavaFileManager;

    34 import javax.tools.ForwardingJavaFileManager;

    35 import javax.tools.FileObject;

    36 import javax.tools.JavaCompiler;

    37 import javax.tools.JavaCompiler.CompilationTask;

    38 import javax.tools.JavaFileManager;

    39 import javax.tools.JavaFileObject;

    40 import javax.tools.JavaFileObject.Kind;

    41 import javax.tools.SimpleJavaFileObject;

    42 import javax.tools.ToolProvider;

    43 

    44 /**

    45  * {@code InMemoryJavaCompiler} can be used for compiling a {@link

    46  * CharSequence} to a {@code byte[]}.

    47  *

    48  * The compiler will not use the file system at all, instead using a {@link

    49  * ByteArrayOutputStream} for storing the byte code. For the source code, any

    50  * kind of {@link CharSequence} can be used, e.g. {@link String}, {@link

    51  * StringBuffer} or {@link StringBuilder}.

    52  *

    53  * The {@code InMemoryCompiler} can easily be used together with a {@code

    54  * ByteClassLoader} to easily compile and load source code in a {@link String}:

    55  *

    56  * <pre>

    57  * {@code

    58  * import com.oracle.java.testlibrary.InMemoryJavaCompiler;

    59  * import com.oracle.java.testlibrary.ByteClassLoader;

    60  *

    61  * class Example {

    62  *     public static void main(String[] args) {

    63  *         String className = "Foo";

    64  *         String sourceCode = "public class " + className + " {" +

    65  *                             "    public void bar() {" +

    66  *                             "        System.out.println("Hello from bar!");" +

    67  *                             "    }" +

    68  *                             "}";

    69  *         byte[] byteCode = InMemoryJavaCompiler.compile(className, sourceCode);

    70  *         Class fooClass = ByteClassLoader.load(className, byteCode);

    71  *     }

    72  * }

    73  * }

    74  * </pre>

    75  */

    76 public class InMemoryJavaCompiler {

    77     private static class MemoryJavaFileObject extends SimpleJavaFileObject {

    78         private final String className;

    79         private final CharSequence sourceCode;

    80         private final ByteArrayOutputStream byteCode;

    81 

    82         public MemoryJavaFileObject(String className, CharSequence sourceCode) {

    83             super(URI.create("string:///" + className.replace('.','/') + Kind.SOURCE.extension), Kind.SOURCE);

    84             this.className = className;

    85             this.sourceCode = sourceCode;

    86             this.byteCode = new ByteArrayOutputStream();

    87         }

    88 

    89         @Override

    90         public CharSequence getCharContent(boolean ignoreEncodingErrors) {

    91             return sourceCode;

    92         }

    93 

    94         @Override

    95         public OutputStream openOutputStream() throws IOException {

    96             return byteCode;

    97         }

    98 

    99         public byte[] getByteCode() {

   100             return byteCode.toByteArray();

   101         }

   102 

   103         public String getClassName() {

   104             return className;

   105         }

   106     }

   107 

   108     private static class FileManagerWrapper extends ForwardingJavaFileManager {

   109         private MemoryJavaFileObject file;

   110 

   111         public FileManagerWrapper(MemoryJavaFileObject file) {

   112             super(getCompiler().getStandardFileManager(null, null, null));

   113             this.file = file;

   114         }

   115 

   116         @Override

   117         public JavaFileObject getJavaFileForOutput(Location location, String className,

   118                                                    Kind kind, FileObject sibling)

   119             throws IOException {

   120             if (!file.getClassName().equals(className)) {

   121                 throw new IOException("Expected class with name " + file.getClassName() +

   122                                       ", but got " + className);

   123             }

   124             return file;

   125         }

   126     }

   127 

   128     /**

   129      * Compiles the class with the given name and source code.

   130      *

   131      * @param className The name of the class

   132      * @param sourceCode The source code for the class with name {@code className}

   133      * @throws RuntimeException if the compilation did not succeed

   134      * @return The resulting byte code from the compilation

   135      */

   136     public static byte[] compile(String className, CharSequence sourceCode) {

   137         MemoryJavaFileObject file = new MemoryJavaFileObject(className, sourceCode);

   138         CompilationTask task = getCompilationTask(file);

   139 

   140         if(!task.call()) {

   141             throw new RuntimeException("Could not compile " + className + " with source code " + sourceCode);

   142         }

   143 

   144         return file.getByteCode();

   145     }

   146 

   147     private static JavaCompiler getCompiler() {

   148         return ToolProvider.getSystemJavaCompiler();

   149     }

   150 

   151     private static CompilationTask getCompilationTask(MemoryJavaFileObject file) {

   152         return getCompiler().getTask(null, new FileManagerWrapper(file), null, null, null, Arrays.asList(file));

   153     }

   154 }