使用Java動態(tài)編譯改善Java代碼及動態(tài)編譯需要注意的問題

public class Client {
     public static void main(String[] args) throws Exception {
         //Java源代碼
         String sourceStr = "public class Hello{    public String sayHello (String name) {return "Hello," + name + "!";}}";
         //類名及文件名
         String clsName = "Hello";
         //方法名
         String methodName = "sayHello";
         //當(dāng)前編譯器
         JavaCompiler cmp = ToolProvider.getSystemJavaCompiler();
         //Java標(biāo)準(zhǔn)文件管理器
         StandardJavaFileManager fm = cmp.getStandardFileManager(null,null,null);
         //Java文件對象
         JavaFileObject jfo = new StringJavaObject(clsName,sourceStr);
         //編譯參數(shù)，類似于javac <options>中的options
         List<String> optionsList = new ArrayList<String>();
         //編譯文件的存放地方，注意：此處是為Eclipse工具特設(shè)的
         optionsList.addAll(Arrays.asList("-d","./bin"));
         //要編譯的單元
         List<JavaFileObject> jfos = Arrays.asList(jfo);
         //設(shè)置編譯環(huán)境
         JavaCompiler.CompilationTask task = cmp.getTask(null, fm, null, optionsList,null,jfos);
         //編譯成功
         if(task.call()){
             //生成對象
             Object obj = Class.forName(clsName).newInstance();
             Class<? extends Object> cls = obj.getClass();
             //調(diào)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對象
class StringJavaObject extends SimpleJavaFileObject{
     //源代碼
     private String content = "";
     //遵循Java規(guī)范的類名及文件
     public StringJavaObject(String _javaFileName,String _content){
           super(_createStringJavaObjectUri(_javaFileName),Kind.SOURCE);
           content = _content;
     }
     //產(chǎn)生一個URL資源路徑
     private static URI _createStringJavaObjectUri(String name){
        //注意此處沒有設(shè)置包名
        return URI.create("String:///" + name + Kind.SOURCE.extension);
     }
     //文本文件代碼
     @Override
     public CharSequence getCharContent(boolean ignoreEncodingErrors)
            throws IOException {
        return content;
    }
}