[改善Java代码]慎用动态编译

1 public class Client {
2 public static void main(String[] args) throws Exception {
3 //Java源代码
4 String sourceStr = "public class Hello{ public String sayHello (String name) {return \"Hello,\" + name + \"!\";}}";
5 //类名及文件名
6 String clsName = "Hello";
7 //方法名
8 String methodName = "sayHello";
9 文章来源地址26882.html //当前编译器
10 JavaCompiler cmp = ToolProvider.getSystemJavaCompiler();
11 //Java标准文件管理器
12 StandardJavaFileManager fm = cmp.getStandardFileManager(null,null,null);
13 //Java文件对象
14 JavaFileObject jfo = new StringJavaObject(clsName,sourceStr);
15 //编译参数，类似于javac 中的options
16 List optiOnsList= new ArrayList();
17 //编译文件的存放地方，注意：此处是为Eclipse工具特设的
18 optionsList.addAll(Arrays.asList("-d","./bin"));
19 //要编译的单元
20 List jfos = Arrays.asList(jfo);
21 //设置编译环境
22 JavaCompiler.CompilationTask task = cmp.getTask(null, fm, null, optionsList,null,jfos);
23 //编译成功
24 if(task.call()){
25 //生成对象
26 Object obj = Class.forName(clsName).newInstance();
27 Classextends Object> cls = obj.getClass();
28 //调用sayHello方法
29 Method m = cls.getMethod(methodName, String.class);
30 String str = (String) m.invoke(obj, "Dynamic Compilation");
31 System.out.println(str);
32 }
33 }
34 }
35 //文本中的Java对象
36 class StringJavaObject extends SimpleJavaFileObject{
37 //源代码
38 private String cOntent= "";
39 //遵循Java规范的类名及文件
40 public StringJavaObject(String _javaFileName,String _content){
41 super(_createStringJavaObjectUri(_javaFileName),Kind.SOURCE);
42 cOntent= _content;
43 }
44 //产生一个URL资源路径
45 private static URI _createStringJavaObjectUri(String name){
46 //注意此处没有设置包名
47 return URI.create("String:///" + name + Kind.SOURCE.extension);
48 }
49 //文本文件代码
50 @Override
51 public CharSequence getCharContent(boolean ignoreEncodingErrors)
52 throws IOException {
53 return content;
54 }
55 }