[英]JavaCompiler works when running the main method directly but not when running spring-boot:run
我有一個非常簡單的spring-boot項目，該項目用於以編程方式將.java文件編譯為.class文件。 神秘的是，它在運行Applicaiton類中的main方法時有效，但在運行spring-boot:run時失敗。
首先，我將說明我在這個項目中擁有的東西：
Compiler.java ：用於將.java文件編譯為.class文件
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);
}
}
我還有一個名為DemoApplicaiton.java的文件，該文件隨SpringBoot Generator一起提供。
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);
}
}
我還將com.google.guava-guava-19.0添加到pom.xml因為要以編程方式編譯的文件需要它。
眾所周知，有兩種方法可以啟動spring-boot項目：
mvn spring-boot:run 我嘗試了第一種方法，並在啟動后嘗試訪問url localhost:8080/compilerTest 。 我得到了{success: true} 。
然后，我嘗試了第二種方法，並嘗試在啟動后訪問相同的URL localhost:8080/compilerTest ，這次失敗，出現錯誤：
/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]
為什么？ 有什么辦法可以使它使用spring-boot:run嗎？
我不完全是為什么，但是我找到了解決這個問題的方法。
在Compiler.java ，替換以下行：
Iterable<String> options = Arrays.asList("-classpath", System.getProperty("user.home") + "/.m2/repository/com/google/guava/guava/19.0/guava-19.0.jar");
與以下之一：
fileManager.setLocation(StandardLocation.CLASS_PATH, System.getProperty("user.home") + "/.m2/repository/com/google/guava/guava/19.0/guava-19.0.jar");
如果要添加多個類路徑，請使用列表：
fileManager.setLocation(StandardLocation.CLASS_PATH, Arrays.asList(new File("/tmp/jar1.jar"), new File("/tmp/jar2.jar")));
我猜規則是，如果使用fileManager.setLocation ， options的-classpath在某些情況下將無法正常工作，我不確定為什么。
這是Compiler.java的完整工作源代碼，以供將來參考。
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;
}
}
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