JavaCompiler在直接运行main方法时有效，但在运行spring-boot：run时无效

Question

I have a very simple spring-boot project, which is used to compile a .java file programmatically to a .class file. What's mysterious is that, it worked when running the main method in the Applicaiton class, but failed when running spring-boot:run .

First I will illustrate what I have in this project:

Compiler.java : used to compile .java files to .class files

package com.example.demo;

import java.io.File;
import java.io.IOException;
import javax.tools.*;
import java.net.URI;
import java.util.Arrays;
import java.util.Collections;

public class Compiler {
    public static void compileTestClass() throws IOException {
        Compiler.compile("com.example.TestClass", "package com.example;\n" +
                "\n" +
                "import com.google.common.collect.ImmutableMap;\n" +
                "\n" +
                "public class TestClass {\n" +
                "}\n", new File("/tmp"));
    }
    public static void compile(String className, String javaSource, File outputDir) throws IOException {
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);

        outputDir.mkdirs();
        Iterable<String> options = Arrays.asList("-classpath", System.getProperty("user.home") + "/.m2/repository/com/google/guava/guava/19.0/guava-19.0.jar");
        fileManager.setLocation(StandardLocation.CLASS_OUTPUT, Collections.singleton(outputDir));

        JavaSourceFromString javaSourceFromString = new JavaSourceFromString(className, javaSource);
        Iterable<? extends JavaFileObject> compilationUnits = Collections.singletonList(javaSourceFromString);
        JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, null, options, null, compilationUnits);
        boolean success = task.call();
        if (!success) {
            throw new RuntimeException("Compilation failed.");
        }
    }
}

/**
 * A file object used to represent source coming from a string.
 */
class JavaSourceFromString extends SimpleJavaFileObject {
    /**
     * The source code of this "file".
     */
    final String code;

    /**
     * Constructs a new JavaSourceFromString.
     *
     * @param name the name of the compilation unit represented by this file object
     * @param code the source code for the compilation unit represented by this file object
     */
    JavaSourceFromString(String name, String code) {
        super(URI.create("string:///" + name.replace('.', '/') + Kind.SOURCE.extension),
                Kind.SOURCE);
        this.code = code;
    }

    @Override
    public CharSequence getCharContent(boolean ignoreEncodingErrors) {
        return code;
    }
}

MainController.java

package com.example.demo;

import com.google.common.collect.ImmutableMap;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.io.IOException;
import java.util.Map;

@RestController
public class MainController {
    @GetMapping("/compilerTest")
    public Map<String, Object> compilerTest() throws IOException {
        Compiler.compileTestClass();
        return ImmutableMap.of("success", true);
    }
}

I also have a file called DemoApplicaiton.java , which is shipped with SpringBoot Generator

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

I also added com.google.guava-guava-19.0 to pom.xml because the file to be compiled programmatically needed it.

As we all know, there are two ways to start a spring-boot project:

1. Run the main method in DemoApplication.java
2. Run mvn spring-boot:run

I tried the first method, and try accessing the url localhost:8080/compilerTest after it started, it worked. I got a {success: true} .

Then I tried the second method, and try accessing the same url localhost:8080/compilerTest after it started, I failed this time, I got an error:

/com/example/TestClass.java:3: error: package com.google.common.collect does not exist
import com.google.common.collect.ImmutableMap;
                                ^
1 error
2018-10-02 11:45:06.002 ERROR 43525 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.RuntimeException: Compilation failed.] with root cause

java.lang.RuntimeException: Compilation failed.
    at com.example.demo.Compiler.compile(Compiler.java:32) ~[classes/:na]
    at com.example.demo.Compiler.compileTestClass(Compiler.java:12) ~[classes/:na]
    at com.example.demo.MainController.compilerTest(MainController.java:14) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_151]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_151]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_151]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_151]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:891) ~[spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) ~[spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) ~[spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974) ~[spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866) ~[spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851) ~[spring-webmvc-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.9.RELEASE.jar:5.0.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_151]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_151]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.34.jar:8.5.34]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_151]

Why? Is there any way to to make it work using spring-boot:run ?

Answer 1

I don't exactly why, but I found a solution to this problem.

In Compiler.java , replace this line:

Iterable<String> options = Arrays.asList("-classpath", System.getProperty("user.home") + "/.m2/repository/com/google/guava/guava/19.0/guava-19.0.jar");

with the following one:

fileManager.setLocation(StandardLocation.CLASS_PATH, System.getProperty("user.home") + "/.m2/repository/com/google/guava/guava/19.0/guava-19.0.jar");

If you want to add multiple class paths, just use a List:

fileManager.setLocation(StandardLocation.CLASS_PATH, Arrays.asList(new File("/tmp/jar1.jar"), new File("/tmp/jar2.jar")));

I guess the rule is, if you use fileManager.setLocation , the -classpath in options will not work in some cases somehow, I'm not sure why.

Here is the complete working source code of Compiler.java , for future reference.

package com.example.demo;

import java.io.File;
import java.io.IOException;
import javax.tools.*;
import java.net.URI;
import java.util.Arrays;
import java.util.Collections;

public class Compiler {
    public static void compileTestClass() throws IOException {
        Compiler.compile("com.example.TestClass", "package com.example;\n" +
                "\n" +
                "import com.google.common.collect.ImmutableMap;\n" +
                "\n" +
                "public class TestClass {\n" +
                "}\n", new File("/tmp"));
    }
    public static void compile(String className, String javaSource, File outputDir) throws IOException {
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);

        outputDir.mkdirs();
        fileManager.setLocation(StandardLocation.CLASS_OUTPUT, Collections.singleton(outputDir));
        fileManager.setLocation(StandardLocation.CLASS_PATH, System.getProperty("user.home") + "/.m2/repository/com/google/guava/guava/19.0/guava-19.0.jar");

        JavaSourceFromString javaSourceFromString = new JavaSourceFromString(className, javaSource);
        Iterable<? extends JavaFileObject> compilationUnits = Collections.singletonList(javaSourceFromString);
        JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, null, options, null, compilationUnits);
        boolean success = task.call();
        if (!success) {
            throw new RuntimeException("Compilation failed.");
        }
    }
}

/**
 * A file object used to represent source coming from a string.
 */
class JavaSourceFromString extends SimpleJavaFileObject {
    /**
     * The source code of this "file".
     */
    final String code;

    /**
     * Constructs a new JavaSourceFromString.
     *
     * @param name the name of the compilation unit represented by this file object
     * @param code the source code for the compilation unit represented by this file object
     */
    JavaSourceFromString(String name, String code) {
        super(URI.create("string:///" + name.replace('.', '/') + Kind.SOURCE.extension),
                Kind.SOURCE);
        this.code = code;
    }

    @Override
    public CharSequence getCharContent(boolean ignoreEncodingErrors) {
        return code;
    }
}