Java example source code file (BridgeHarness.java)

This example Java source code file (BridgeHarness.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bridge, bridgefinder, bridgeharness, bridges, error, exception, javafileobject, list, map, method, redundant, typeelement, util

The BridgeHarness.java Java example source code

/*
 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * @test
 * @bug 8013789
 * @summary Compiler should emit bridges in interfaces
 * @library /tools/javac/lib
 * @build JavacTestingAbstractProcessor BridgeHarness
 * @run main BridgeHarness
 */

import com.sun.source.util.JavacTask;
import com.sun.tools.classfile.AccessFlags;
import com.sun.tools.classfile.ClassFile;
import com.sun.tools.classfile.ConstantPool;
import com.sun.tools.classfile.ConstantPoolException;
import com.sun.tools.classfile.Method;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import com.sun.tools.javac.util.List;

import java.io.File;
import java.io.InputStream;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;

import static javax.tools.StandardLocation.*;

public class BridgeHarness {

    /** number of errors found (must be zero for the test to pass) */
    static int nerrors = 0;

    /** the (shared) Java compiler used for compiling the tests */
    static final JavaCompiler comp = ToolProvider.getSystemJavaCompiler();

    /** the (shared) file manager used by the compiler */
    static final StandardJavaFileManager fm = comp.getStandardFileManager(null, null, null);

    public static void main(String[] args) throws Exception {
        //set sourcepath
        fm.setLocation(SOURCE_PATH,
                Arrays.asList(new File(System.getProperty("test.src"), "tests")));
        //set output (-d)
        fm.setLocation(javax.tools.StandardLocation.CLASS_OUTPUT,
                Arrays.asList(new File(System.getProperty("user.dir"))));
        for (JavaFileObject jfo : fm.list(SOURCE_PATH, "", Collections.singleton(JavaFileObject.Kind.SOURCE), true)) {
            //for each source, compile and check against annotations
            new BridgeHarness(jfo).compileAndCheck();
        }
        //if there were errors, fail
        if (nerrors > 0) {
            throw new AssertionError("Errors were found");
        }
    }

    /* utility methods */

    /**
     * Remove an element from a list
     */
    static <Z> List drop(List lz, Z z) {
        if (lz.head == z) {
            return drop(lz.tail, z);
        } else if (lz.isEmpty()) {
            return lz;
        } else {
            return drop(lz.tail, z).prepend(lz.head);
        }
    }

    /**
     * return a string representation of a bytecode method
     */
    static String descriptor(Method m, ConstantPool cp) throws ConstantPoolException {
        return m.getName(cp) + m.descriptor.getValue(cp);
    }

    /* test harness */

    /** Test file to be compiled */
    JavaFileObject jfo;

    /** Mapping between class name and list of bridges in class with that name */
    Map<String, List bridgesMap = new HashMap>();

    protected BridgeHarness(JavaFileObject jfo) {
        this.jfo = jfo;
    }

    /**
     * Compile a test using a custom annotation processor and check the generated
     * bytecode against discovered annotations.
     */
    protected void compileAndCheck() throws Exception {
        JavacTask ct = (JavacTask)comp.getTask(null, fm, null, null, null, Arrays.asList(jfo));
        ct.setProcessors(Collections.singleton(new BridgeFinder()));

        for (JavaFileObject jfo : ct.generate()) {
            checkBridges(jfo);
        }
    }

    /**
     * Check that every bridge in the generated classfile has a matching bridge
     * annotation in the bridge map
     */
    protected void checkBridges(JavaFileObject jfo) {
        try (InputStream is = jfo.openInputStream()) {
            ClassFile cf = ClassFile.read(is);
            System.err.println("checking: " + cf.getName());

            List<Bridge> bridgeList = bridgesMap.get(cf.getName());
            if (bridgeList == null) {
                //no bridges - nothing to check;
                bridgeList = List.nil();
            }

            for (Method m : cf.methods) {
                if (m.access_flags.is(AccessFlags.ACC_SYNTHETIC | AccessFlags.ACC_BRIDGE)) {
                    //this is a bridge - see if there's a match in the bridge list
                    Bridge match = null;
                    for (Bridge b : bridgeList) {
                        if (b.value().equals(descriptor(m, cf.constant_pool))) {
                            match = b;
                            break;
                        }
                    }
                    if (match == null) {
                        error("No annotation for bridge method: " + descriptor(m, cf.constant_pool));
                    } else {
                        bridgeList = drop(bridgeList, match);
                    }
                }
            }
            if (bridgeList.nonEmpty()) {
                error("Redundant bridge annotation found: " + bridgeList.head.value());
            }
        } catch (Exception e) {
            e.printStackTrace();
            throw new Error("error reading " + jfo.toUri() +": " + e);
        }
    }

    /**
     * Log an error
     */
    protected void error(String msg) {
        nerrors++;
        System.err.printf("Error occurred while checking file: %s\nreason: %s\n", jfo.getName(), msg);
    }

    /**
     * This annotation processor is used to populate the bridge map with the
     * contents of the annotations that are found on the tests being compiled
     */
    @SupportedAnnotationTypes({"Bridges","Bridge"})
    class BridgeFinder extends JavacTestingAbstractProcessor {
        @Override
        public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
            if (roundEnv.processingOver())
                return true;

            TypeElement bridgeAnno = elements.getTypeElement("Bridge");
            TypeElement bridgesAnno = elements.getTypeElement("Bridges");

            //see if there are repeated annos
            for (Element elem: roundEnv.getElementsAnnotatedWith(bridgesAnno)) {
                List<Bridge> bridgeList = List.nil();
                Bridges bridges = elem.getAnnotation(Bridges.class);
                for (Bridge bridge : bridges.value()) {
                    bridgeList = bridgeList.prepend(bridge);
                }
                bridgesMap.put(((ClassSymbol)elem).flatname.toString(), bridgeList);
            }

            //see if there are non-repeated annos
            for (Element elem: roundEnv.getElementsAnnotatedWith(bridgeAnno)) {
                Bridge bridge = elem.getAnnotation(Bridge.class);
                bridgesMap.put(((ClassSymbol)elem).flatname.toString(),
                        List.of(bridge));
            }

            return true;
        }
    }
}