ToolProvider.getSystemJavaCompiler() returns null

问题:

I am trying to use the JavaCompiler class:

• http://docs.oracle.com/javase/6/docs/api/javax/tools/JavaCompiler.html

When I call ToolProvider.getSystemJavaCompiler() it returns null.

I think this is because I'm using a JRE instead of a JDK.

The problem is I want it to run on all platforms regardless of weather the user is using a JRE or a JDK.

If anyone knows how to fix this, or an alternative method to use please comment.

Any help would be appreciated.

回答1:

ToolProvider.getSystemJavaCompiler() is not available.

Is tools.jar missing from the classpath?

Set class path to the tools.jar file which can found in jdk\jre directory.

System.setProperty("java.home", "C:\\Program Files\\Java\\jdk1.7.0_02");

回答2:

I think this is the problem .Explicitly specifying the version of java.exe you're using as the one in your JDK directory.

see here for details

回答3:

Here is how to run the Java compiler from your application when there is no JDK installed.

First, include the tools.jar file from a JDK with your Java app and put tools.jar in your classpath. Oracle probably won't like you doing that. But, there is legal work-around. You get the tools.jar file from the free JDKs offered by openjdk.org (openjdk), RedHat (IcedTea), or Azul Systems (Zulu).

Next, instead of using ToolProvider.getSystemJavaCompiler() and the JavaCompiler class, call the compiler located in tools.jar directly. Below is snippet of code:

String classpath = ...; // make sure tools.jar is in this path 
String sourcepath = ...; // path to your sources
String putputpath = ...; // directory for generated class files
String filepath = ...; // file path the file you want to compile

String[] args = new String[] {
"-classpath", classpath,
"-sourcepath", sourcepath,
"-d", putputpath,
filePath
};
com.sun.tools.javac.Main javac = new com.sun.tools.javac.Main();
int compileStatus = javac.compile(args);

回答4:

Just copy tools.jar file from /lib to It works

You can obtain by System.out.println( System.getProperty( "java.home"))

Most of time it is like C:\Program files\Java\jre(version) [ for windows ]

回答5:

Another solution is from: - http://bugs.java.com/bugdatabase/view_bug.do?bug_id=7181951

Copy tools.jar in JDK_HOME/lib/ into JRE_HOME/lib/. At least to me, it solved my issue magically!

(I did nothing recommended as above. I just copied it there.)

回答6:

here is simple solution that worked for me

I just changed the jre System library to .....Program Files\Java\jdk1.7.0_55\jre instead of ....Program Files\Java\jdk1.7.0_55\bin and it worked for me.

回答7:

On a Mac this worked for me:

  System.setProperty("java.home", "/Library/Java/JavaVirtualMachines/jdk1.8.0_144.jdk/Contents/Home");
  javax.tools.JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

(It does not work for idk 10 for some reason).

回答8:

I had both JRE and JDK in my buildPath...i just removed the JRE and it fixed.