从字符串编译Java代码会导致ClassNotFoundException
我正在尝试一个代码示例,它使用javax.tools编译字符串中的代码。Class.forName导致ClassNotFoundException。有人知道为什么吗?我正在使用Java7从字符串编译Java代码会导致ClassNotFoundException,java,java-compiler-api,Java,Java Compiler Api,我正在尝试一个代码示例,它使用javax.tools编译字符串中的代码。Class.forName导致ClassNotFoundException。有人知道为什么吗?我正在使用Java7 import java.io.IOException; import java.io.PrintWriter; import java.io.StringWriter; import java.lang.reflect.InvocationTarg
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.InvocationTargetException;
import java.net.URI;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import javax.tools.Diagnostic;
import javax.tools.DiagnosticCollector;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
import javax.tools.ToolProvider;
import javax.tools.JavaCompiler.CompilationTask;
public class Main {
public static void main(String args[]) throws IOException {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println("public class HelloWorld {");
out.println(" public static void main(String args[]) {");
out.println(" System.out.println(\"This is in another java file\");");
out.println(" }");
out.println("}");
out.close();
JavaFileObject file = new JavaSourceFromString("HelloWorld", writer.toString());
Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(file);
CompilationTask task = compiler.getTask(null, null, diagnostics, optionList, null, compilationUnits);
boolean success = task.call();
for (Diagnostic diagnostic : diagnostics.getDiagnostics()) {
System.out.println(diagnostic.getCode());
System.out.println(diagnostic.getKind());
System.out.println(diagnostic.getPosition());
System.out.println(diagnostic.getStartPosition());
System.out.println(diagnostic.getEndPosition());
System.out.println(diagnostic.getSource());
System.out.println(diagnostic.getMessage(null));
}
System.out.println("Success: " + success);
if (success) {
try {
Class.forName("HelloWorld").getDeclaredMethod("main", new Class[] { String[].class })
.invoke(null, new Object[] { null });
} catch (ClassNotFoundException e) {
System.err.println("Class not found: " + e);
} catch (NoSuchMethodException e) {
System.err.println("No such method: " + e);
} catch (IllegalAccessException e) {
System.err.println("Illegal access: " + e);
} catch (InvocationTargetException e) {
System.err.println("Invocation target: " + e);
}
}
}
}
class JavaSourceFromString extends SimpleJavaFileObject {
final String code;
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;
}
}
import java.io.IOException;
导入java.io.PrintWriter;
导入java.io.StringWriter;
导入java.lang.reflect.InvocationTargetException;
导入java.net.URI;
导入java.util.ArrayList;
导入java.util.array;
导入java.util.List;
导入javax.tools.Diagnostic;
导入javax.tools.DiagnosticCollector;
导入javax.tools.JavaCompiler;
导入javax.tools.JavaFileObject;
导入javax.tools.SimpleJavaFileObject;
导入javax.tools.ToolProvider;
导入javax.tools.JavaCompiler.CompilationTask;
公共班机{
公共静态void main(字符串args[])引发IOException{
JavaCompiler=ToolProvider.getSystemJavaCompiler();
DiagnosticCollector diagnostics=新建DiagnosticCollector();
StringWriter编写器=新的StringWriter();
PrintWriter out=新的PrintWriter(writer);
println(“公共类HelloWorld{”);
println(“publicstaticvoidmain(stringargs[]){”);
println(“System.out.println(\“这在另一个java文件中\”);”;
out.println(“}”);
out.println(“}”);
out.close();
JavaFileObject file=newJavaSourceFromString(“HelloWorld”,writer.toString());
Iterable类加载器不知道您的HelloWorld
类。您可以这样做:
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { root.toURI().toURL() }); //root is path to class file
Class<?> cls = Class.forName("HelloWorld", true, classLoader);
URLClassLoader classLoader=URLClassLoader.newInstance(新URL[]{root.toURI().toURL()});//root是类文件的路径
Class cls=Class.forName(“HelloWorld”,true,classLoader);
您可以看到。这意味着只有一件事:HelloWorld
类不在类路径上。生成的类不应保存到磁盘。我搜索的解决方案似乎是:此博客帖子已消失。可通过archive.org访问: