使用Java动态编译改善Java代码及动态编译需要注意的问题

public class Client {
     public static void main(String[] args) throws Exception {
         //Java源代码
         String sourceStr = "public class Hello{    public String sayHello (String name) {return "Hello," + name + "!";}}";
         //类名及文件名
         String clsName = "Hello";
         //方法名
         String methodName = "sayHello";
         //当前编译器
         JavaCompiler cmp = ToolProvider.getSystemJavaCompiler();
         //Java标准文件管理器
         StandardJavaFileManager fm = cmp.getStandardFileManager(null,null,null);
         //Java文件对象
         JavaFileObject jfo = new StringJavaObject(clsName,sourceStr);
         //编译参数，类似于javac <options>中的options
         List<String> optionsList = new ArrayList<String>();
         //编译文件的存放地方，注意：此处是为Eclipse工具特设的
         optionsList.addAll(Arrays.asList("-d","./bin"));
         //要编译的单元
         List<JavaFileObject> jfos = Arrays.asList(jfo);
         //设置编译环境
         JavaCompiler.CompilationTask task = cmp.getTask(null, fm, null, optionsList,null,jfos);
         //编译成功
         if(task.call()){
             //生成对象
             Object obj = Class.forName(clsName).newInstance();
             Class<? extends Object> cls = obj.getClass();
             //调用sayHello方法
             Method m = cls.getMethod(methodName, String.class);
             String str = (String) m.invoke(obj, "Dynamic Compilation");
             System.out.println(str);
        }
    }
}
//文本中的Java对象
class StringJavaObject extends SimpleJavaFileObject{
     //源代码
     private String content = "";
     //遵循Java规范的类名及文件
     public StringJavaObject(String _javaFileName,String _content){
           super(_createStringJavaObjectUri(_javaFileName),Kind.SOURCE);
           content = _content;
     }
     //产生一个URL资源路径
     private static URI _createStringJavaObjectUri(String name){
        //注意此处没有设置包名
        return URI.create("String:///" + name + Kind.SOURCE.extension);
     }
     //文本文件代码
     @Override
     public CharSequence getCharContent(boolean ignoreEncodingErrors)
            throws IOException {
        return content;
    }
}