在下面的示例中,我尝试使用sun.tools.javac.Main
动态编译我生成的类,然后实例化该类的对象并调用方法。到目前为止,我什至无法通过加载生成的类。我在 Eclipse 中遇到以下异常:
java.lang.ClassNotFoundException: TestHello_1289950330167
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at MyClassGenerator.runIt(MyClassGenerator.java:47)
at MyClassGenerator.main(MyClassGenerator.java:13)
Note: sun.tools.javac.Main has been deprecated.
1 warning
Running TestHello_1289950330167:
这是代码:
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileWriter;
import java.net.URL;
import java.net.URLClassLoader;
public class MyClassGenerator {
String generatedClassName = "TestHello_" + System.currentTimeMillis();
String javaFileName = this.generatedClassName + ".java";
public static void main(final String args[]) {
final MyClassGenerator mtc = new MyClassGenerator();
mtc.createIt();
if (mtc.compileIt()) {
System.out.println("Running " + mtc.generatedClassName + ":\n\n");
mtc.runIt();
}
else {
System.out.println(mtc.javaFileName + " is bad.");
}
}
public void loadIt() {
final ClassLoader classLoader = MyClassGenerator.class.getClassLoader();
try {
final Class aClass = classLoader.loadClass(this.generatedClassName);
System.out.println("Loaded " + aClass.getName());
}
catch (final ClassNotFoundException e) {
e.printStackTrace();
}
}
public void createIt() {
try {
final FileWriter aWriter = new FileWriter(this.javaFileName, true);
aWriter.write("public class " + this.generatedClassName + " { }");
aWriter.flush();
aWriter.close();
}
catch (final Exception e) {
e.printStackTrace();
}
}
public boolean compileIt() {
final String[] source = { new String(this.javaFileName) };
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
new sun.tools.javac.Main(baos, source[0]).compile(source);
System.out.print(baos.toString());
return (baos.toString().indexOf("error") == -1);
}
public void runIt() {
try {
final File file = new File(this.javaFileName);
final URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { file.toURI().toURL() });
final Class<?> cls = Class.forName(this.generatedClassName, true, classLoader);
}
catch (final Exception e) {
e.printStackTrace();
}
}
}
因为它不在类路径中。将其写入类路径(或将其根路径添加到类路径)或使用URLClassLoader http://download.oracle.com/javase/6/docs/api/java/net/URLClassLoader.html.
File root = new File(".");
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[] { root.toURI().toURL() });
Class<?> cls = Class.forName(generatedClassName, true, classLoader);
在中使用相对路径java.io
顺便说一句,这是一个坏主意。您依赖于当前工作目录,该目录无法在代码中控制。
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