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      1 /*
      2  * Copyright (C) 2018 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.javac;
     18 
     19 import com.google.common.io.Files;
     20 
     21 import java.util.stream.Collectors;
     22 import org.apache.bcel.classfile.ClassParser;
     23 import org.apache.bcel.classfile.JavaClass;
     24 
     25 import java.io.File;
     26 import java.io.IOException;
     27 import java.io.InputStream;
     28 import java.net.URI;
     29 import java.util.ArrayList;
     30 import java.util.Arrays;
     31 import java.util.List;
     32 import java.util.Locale;
     33 
     34 import javax.tools.DiagnosticCollector;
     35 import javax.tools.JavaCompiler;
     36 import javax.tools.JavaFileObject;
     37 import javax.tools.SimpleJavaFileObject;
     38 import javax.tools.StandardJavaFileManager;
     39 import javax.tools.StandardLocation;
     40 import javax.tools.ToolProvider;
     41 
     42 /**
     43  * Helper class for compiling snippets of Java source and providing access to the resulting class
     44  * files.
     45  */
     46 public class Javac {
     47 
     48     private final JavaCompiler mJavac;
     49     private final StandardJavaFileManager mFileMan;
     50     private final List<JavaFileObject> mCompilationUnits;
     51     private final File mClassOutDir;
     52 
     53     public Javac() throws IOException {
     54         mJavac = ToolProvider.getSystemJavaCompiler();
     55         mFileMan = mJavac.getStandardFileManager(null, Locale.US, null);
     56         mClassOutDir = Files.createTempDir();
     57         mFileMan.setLocation(StandardLocation.CLASS_OUTPUT, Arrays.asList(mClassOutDir));
     58         mFileMan.setLocation(StandardLocation.CLASS_PATH, Arrays.asList(mClassOutDir));
     59         mCompilationUnits = new ArrayList<>();
     60     }
     61 
     62     private String classToFileName(String classname) {
     63         return classname.replace('.', '/');
     64     }
     65 
     66     public Javac addSource(String classname, String contents) {
     67         JavaFileObject java = new SimpleJavaFileObject(URI.create(
     68                 String.format("string:///%s.java", classToFileName(classname))),
     69                 JavaFileObject.Kind.SOURCE
     70                 ){
     71             @Override
     72             public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
     73                 return contents;
     74             }
     75         };
     76         mCompilationUnits.add(java);
     77         return this;
     78     }
     79 
     80     public void compile() {
     81         DiagnosticCollector<JavaFileObject> diagnosticCollector = new DiagnosticCollector<>();
     82         JavaCompiler.CompilationTask task = mJavac.getTask(
     83                 null,
     84                 mFileMan,
     85                 diagnosticCollector,
     86                 null,
     87                 null,
     88                 mCompilationUnits);
     89         boolean result = task.call();
     90         if (!result) {
     91             throw new IllegalStateException(
     92                 "Compilation failed:" +
     93                     diagnosticCollector.getDiagnostics()
     94                         .stream()
     95                         .map(Object::toString)
     96                         .collect(Collectors.joining("\n")));
     97         }
     98     }
     99 
    100     public InputStream getClassFile(String classname) throws IOException {
    101         Iterable<? extends JavaFileObject> objs = mFileMan.getJavaFileObjects(
    102                 new File(mClassOutDir, String.format("%s.class", classToFileName(classname))));
    103         if (!objs.iterator().hasNext()) {
    104             return null;
    105         }
    106         return objs.iterator().next().openInputStream();
    107     }
    108 
    109     public JavaClass getCompiledClass(String classname) throws IOException {
    110         return new ClassParser(getClassFile(classname),
    111                 String.format("%s.class", classToFileName(classname))).parse();
    112     }
    113 }
    114