在java代码中经常有读取外部资源的要求:如配置文件等等,通常会把配置文件放在classpath下或者在web项目中放在web-inf下.

1.从当前的工作目录中读取:

try{

BufferedReader in= new BufferedReader(new InputStreamReader(new FileInputStream("wkdir.txt")));

String str;while ((str = in.readLine()) != null) {

System.out.println(str);

}

in.close();

}catch(IOException e) {}

2.从classpath中读取(读取找到的第一个符合名称的文件):

try{

InputStream stream= ClassLoader.getSystemResourceAsStream("fileinjar.txt");

BufferedReader in= new BufferedReader(newInputStreamReader(stream));

String str;while ((str = in.readLine()) != null) {

System.out.println(str);

}

in.close();

}catch (IOException e) {}

3.从classpath中读取(读取找到的所有符合名称的文件,如Spring中带有classpath*:前缀的情况就会从classpath中遍历):

try{

Enumeration resourceUrls= Thread.currentThread().getContextClassLoader().getResources("fileinjar.txt");while(resourceUrls.hasMoreElements()) {

URL url=(URL) resourceUrls.nextElement();

System.out.println(url);

BufferedReader in= new BufferedReader(newInputStreamReader(url.openStream()));

String str;while ((str = in.readLine()) != null) {

System.out.println(str);

}

in.close();

}

}catch (IOException e) {}

4.从URL中读取:

try{

URL url= new URL("http://blog.csdn.net/kkdelta");

System.out.println(url);

BufferedReader in= new BufferedReader(newInputStreamReader(url.openStream()));

String str;while ((str = in.readLine()) != null) {

System.out.println(str);

}

in.close();

}catch(IOException e) {

e.printStackTrace();

}

5.web项目从web-inf文件夹读取(通过得到ServletContext读取,可以在servlet或者能够得到request的类中使用):

try{

URL url= (URL) getServletContext().getResource("/WEB-INF/webinffile.txt");//URL url = (URL)req.getSession().getServletContext().getResource("/WEB-INF/webinffile.txt");

System.out.println(url);

BufferedReader in= new BufferedReader(newInputStreamReader(url.openStream()));

String str;while ((str = in.readLine()) != null) {

System.out.println(str);

}

in.close();

}catch(IOException e) {

e.printStackTrace();

}

以上代码在eclipse环境中运行测试过.不过最近在用JUnit的时候,通过ant运行JUnit时通过ClassLoader.getSystemResourceAsStream("file.txt");的方式去找不到文件.改成 Xclass.class.getClassLoader().getResourceAsStream("file.txt");能从ant指定的classpath中找到文件.