Java编译器API NullPointerException [英] Java Compiler API NullPointerException

问题描述

我使用这个代码在运行时编译一个Java文件。首先，这是我的目录树（在Eclipse中）。

I am using this code to compile a Java file at runtime. First of all, here is my directory tree (in Eclipse).

+---- src
+----- package
+------ Compile.java
+
+
+---- temp
+----- anotherpackage
+------ Temp.java (file to compile)

我的代码中我得到NullPointerException（我已经尝试使用JDK作为我的标准VM在Eclipse中）。

Here is my code where I am getting the NullPointerException (I already tried using JDK as my Standard VM in Eclipse).

public static void compile(URI path, InputStream is, OutputStream os, OutputStream err) throws IOException {
    SimpleJavaFileObject source = new CustomJavaFileObject(path, Kind.SOURCE);
    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
    JavaCompiler.CompilationTask task = compiler.getTask(new PrintWriter(err), null, null, null, null, Arrays.asList(source));
    task.call();
}

这里是CustonJavaFileObject：

Here is the CustonJavaFileObject:

class CustomJavaFileObject extends SimpleJavaFileObject {
    protected CustomJavaFileObject(URI uri, Kind kind) {
        super(uri, kind);
    }
}

我做错了什么？

EDIT：

我在我的PATH中没有JDK it）

I do not have the JDK in my PATH (and I can't add it)

这是我的堆栈跟踪：

java.lang.NullPointerException 
  at package.Compiler.compile(Compiler.java:20)
  at package.Interactive.main(Interactive.java:19)

推荐答案

JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); 

会导致问题。指向你的JRE在JDK内部，与jdk不同，jre不提供任何工具。

causes the issue. Point your JRE to be inside the JDK as unlike jdk, jre does not provide any tools.

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