我有一个关于 java.lang.NoSuchMethodError 的问题。这个程序是关于编译器 API (JSR 199)。当我为此创建原型时，它运行工作，但是当我尝试使其成为库时，它会抛出 NoSuchMethodError 异常。
这是第一个原型：
public class DynaCompTest {
public static void main(String[] args) {
String fullName = "HelloWorld";
StringBuilder sourceCode = new StringBuilder();
sourceCode.append("public class HelloWorld {\n")
.append("\tpublic static void main(String[] args) {\n")
.append("\t\tSystem.out.println(\"Hello World\")\n")
.append("\t}\n")
.append("}");
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
JavaFileManager fileManager = new ClassFileManager(compiler.getStandardFileManager(null, null, null));
DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
List<JavaFileObject> jFiles = new ArrayList<>();
jFiles.add(new CharSequenceJavaFileObject(fullName, sourceCode));
compiler.getTask(null, fileManager, diagnostics, null, null, jFiles).call();
for (Diagnostic diagnostic : diagnostics.getDiagnostics()) {
System.out.format("Error on line %d in %s\n", diagnostic.getLineNumber(), diagnostic);
}
}
}
public class CharSequenceJavaFileObject extends SimpleJavaFileObject {
private CharSequence content;
public CharSequenceJavaFileObject(String className, CharSequence content) {
super(URI.create("string:///" + className.replace('.', '/') + Kind.SOURCE.extension), Kind.SOURCE);
this.content = content;
}
@Override
public CharSequence getCharContent(boolean ignoreEncodingErrors) {
return content;
}
}
public class ClassFileManager extends ForwardingJavaFileManager {
private JavaClassObject jClassObject;
public ClassFileManager(StandardJavaFileManager standardManager) {
super(standardManager);
}
@Override
public ClassLoader getClassLoader(Location location) {
return new SecureClassLoader() {
@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
byte[] b = jClassObject.getBytes();
return super.defineClass(name, jClassObject.getBytes(), 0, b.length);
}
};
}
@Override
public JavaFileObject getJavaFileForOutput(Location location, String className, Kind kind, FileObject sibling) throws IOException {
jClassObject = new JavaClassObject(className, kind);
return jClassObject;
}
}
public class JavaClassObject extends SimpleJavaFileObject {
protected final ByteArrayOutputStream bos = new ByteArrayOutputStream();
public JavaClassObject(String name, Kind kind) {
super(URI.create("string:///" + name.replace('.', '/') + kind.extension), kind);
}
public byte[] getBytes() {
return bos.toByteArray();
}
@Override
public OutputStream openOutputStream() {
return bos;
}
}
我将 DynaCompTest 更改为库的 DynamicCompiler：
public class DynamicCompiler {
private JavaCompiler compiler;
private JavaFileManager fileManager;
private List<JavaFileObject> jFiles;
private DiagnosticCollector<JavaFileObject> diagnostics;
public DiagnosticCollector<JavaFileObject> getDiagnostics() {
return diagnostics;
}
public DynamicCompiler(String className, StringBuilder sourceCode) {
compiler = ToolProvider.getSystemJavaCompiler();
fileManager = new ClassFileManager(compiler.getStandardFileManager(null, null, null));
diagnostics = new DiagnosticCollector<>();
jFiles = new ArrayList<>();
jFiles.add(new CharSequenceJavaFileObject(className, sourceCode));
}
public boolean doCompilation() {
return compiler.getTask(null, fileManager, diagnostics, null, null, jFiles).call();
}
}
我创建了第二个原型来测试库：
public class Compiler {
private static StringBuilder sourceCode = new StringBuilder();
public static void main(String[] args) {
boolean status;
sourceCode.append("public class HelloWorld {\n")
.append("\tpublic static void main(String[] args) {\n")
.append("\t\tSystem.out.println(\"Hello World\");\n")
.append("\t}\n")
.append("}");
DynamicCompiler compiler = new DynamicCompiler("HelloWorld", sourceCode);
status = compiler.doCompilation();
StringBuilder messages = new StringBuilder();
if (!status) {
for (Diagnostic diagnostic : compiler.getDiagnostics().getDiagnostics()) {
messages.append("Error on line ")
.append(diagnostic.getLineNumber())
.append(" in ")
.append(diagnostic)
.append("\n");
}
} else {
messages.append("BUILD SUCCESSFUL ");
}
System.out.println(messages.toString());
}
}
当我用上面的代码进行测试时，它运行良好并打印BUILD SUCCESSFUL，但是当我试图让它出错时，例如我删除了;第一个原型一样的分号，它在访问compiler.getDiagnostics().getDiagnostics()循环内部时抛出 NoSuchMethodError 异常。
问题是，为什么在第一个原型中它在尝试出错时运行良好，但当我尝试使用自己的库时它变成异常？
编辑
这是堆栈跟踪：
/HelloWorld.java:3: error: ';' expected
System.out.println("Hello World")
^
1 error
Exception in thread "main" java.lang.NoSuchMethodError: org.ert.lib.DynamicCompiler.getDiagnostics()Ljavax/tools/DiagnosticCollector;
at org.ert.exp.Compiler.main(Compiler.java:28)
Java Result: 1
它应该是这样的：
Error on line 3 in /HelloWorld.java:3: error: ';' expected
System.out.println("Hello World")
^
在尝试调试它时，它显示了一个错误：
public DiagnosticCollector<JavaFileObject> getDiagnostics() {
return diagnostics; // Set Breakpoint here
}
这是错误消息：
Not able to submit breakpoint LineBreakpoint DynamicCompiler.java : 25, reason: No executable location available at line 25 in class org.ert.lib.DynamicCompiler.
Invalid LineBreakpoint DynamicCompiler.java : 25
更新
遇到问题了，如果我们添加整个项目而不是构建库的jar，就会出现这个问题。因此，当我构建库 jar 时，它可以工作。但是任何人都可以解释为什么当我尝试添加整个项目而不是 jar 文件时会发生这种情况？
笔记
我正在使用：
- 来自 Oracle 的 JDK 1.7
- 网豆 7.1.1