Java 编译器一直说 "error while writing className: className.class (Permission denied)"

Question

我正在为我的大学开发一个 Tomcat Web 应用程序，它使学生能够编译他们的 Java 代码并查看跟踪。我正在将它安装在 RHEL7 VM 上。但是当我测试编译功能时（这个不是我实现的），我提供的方法returns this:

error while writing className: className.class (Permission denied)
Error on line 1 in className.java

我将向您展示我认为生成此内容的方法：

public String compileJavaCode(String javaCode, String javaFileName, File workingDir) throws IOException, TimeoutException{

    javax.tools.JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
    DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
    StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null);
    this.createJavaFile(javaCode, javaFileName, workingDir);
    JavaFileObject file = new JavaSourceFromString(javaFileName, javaCode);

    Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(file);
    compiler.getTask(null, fileManager, diagnostics, null, null, compilationUnits).call();

    String diagn = "";
    for ( Diagnostic<? extends JavaFileObject> diagnostic : diagnostics.getDiagnostics()){
        diagn+=diagnostic.getMessage(null)+"\n";//E.g. cannot find symbol symbol: variable variablename
        diagn+="Error on line "+Long.toString(diagnostic.getLineNumber())+" in "+diagnostic.getSource().toUri();//E.g. Error on line 22 in ClassName.java
    }
       fileManager.close();
       compiler.run(null, null, null, workingDir.getAbsolutePath()+File.separator+javaFileName);
       return diagn;
}

学生将在提交代码时看到 diagn 变量的内容。

有趣的是，我设法在 workingDir 目录中获取了 className.class，但我不断从上面的 for 循环中收到该错误。问题可能是compiler.getTask(...).call()？我的意思是也许 compiler.run 能够正确生成 .class 但 compiler.getTask(...).call() 正试图将 .class 写入其他我没有写入权限的地方。

P.S。这是一个非常遗留的代码，所以请对它手下留情。 :)

正如@Alexander 所问，这是 Java 文件的内容：

public class Sommatore {

    public int somma(int i, int j) {
        return i+j;
    }

    public int differenza(int i, int j) {
        return i-j;
    }
}

Answer 1

您使用的用户似乎没有写入目标文件夹的权限。 workingDir 的权限是什么？

Fun fact is that i manage to get the className.class in the workingDir directory but i keep getting that error from the for cycle above. Could the problem be the compiler.getTask(...).call()? I mean maybe compiler.run is able to generate the .class correctly but the compiler.getTask(...).call() is trying to write the .class somewhere else i don't have permission to write in.

为了验证是否属实，您可以新建一个具有开放权限的文件夹试试。例如，您可以尝试使用 as workingDir = /tmp 并检查会发生什么。

编辑

我试图复制你的代码：

    public class JavaCompiler {
    public static void main(String args[]) throws IOException, TimeoutException {
        File dir = new File(System.getProperty("user.dir") + "/src/main/java/");
        System.out.println(compileJavaCode(dir));
    }
    public static String compileJavaCode(File workingDir) throws IOException,      TimeoutException {

        javax.tools.JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
        StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null);
      //    this.createJavaFile(javaCode, javaFileName, workingDir);
      //    JavaFileObject file = new JavaSourceFromString(javaFileName, javaCode);

        Iterable<? extends JavaFileObject> compilationUnits = fileManager
                .getJavaFileObjectsFromStrings(Arrays.asList(System.getProperty("user.dir") + "/src/main/java/Foo.java"));
//    Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(file);
        compiler.getTask(null, fileManager, diagnostics, null, null, compilationUnits).call();

        String diagn = "";
        for (Diagnostic<? extends JavaFileObject> diagnostic : diagnostics.getDiagnostics()) {
            diagn += diagnostic.getMessage(null) + "\n";//E.g. cannot find symbol symbol: variable variablename
            diagn += "Error on line " + Long.toString(diagnostic.getLineNumber()) + " in " + diagnostic.getSource().toUri();//E.g. Error on line 22 in ClassName.java
        }
        fileManager.close();
        compiler.run(null, null, null, workingDir.getAbsolutePath() + File.separator + "Foo.java");
        return diagn;
    }
}

与Foo.java

public class Foo {

    public int somma(int i, int j) {
        return i+j;
    }

    public int differenza(int i, int j) {
        return i-j;
    }
}

有一些变化，但结果应该是一样的。我注意到 "path" 是在

中指定的

File workingDir

将在

中使用

compiler.run(null, null, null, workingDir.getAbsolutePath() + File.separator + "Foo.java");

并在

JavaFileObject file = new JavaSourceFromString(javaFileName, javaCode);
Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(file);

在我的示例中：

Iterable<? extends JavaFileObject> compilationUnits = fileManager
.getJavaFileObjectsFromStrings(Arrays.asList(System.getProperty("user.dir") + "/src/main/java/Foo.java"));

包含你的内容

workingDir

和"file"?

JavaFileObject file = new JavaSourceFromString(javaFileName, javaCode);

在我的情况下，都是一样的。

我尝试用不同的用户执行代码，如果我使用无法写入此文件夹的用户，我会得到

/tmp/testSO/src/main/java/Foo.java:5: error: error while writing Foo: /tmp/testSO/src/main/java/Foo.class (Permission denied)
public class Foo {
       ^
1 error
error while writing Foo: /tmp/testSO/src/main/java/Foo.class (Permission denied)
Error on line 5 in file:/tmp/testSO/src/main/java/Foo.java

Java 编译器一直说 "error while writing className: className.class (Permission denied)"

Java Compiler keeps saying "error while writing className: className.class (Permission denied)"

java

compiler-errors

web-applications

rhel

compiler-warnings