JAVA读取外部资源的方法

JAVA读取外部资源的方法

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:【达内就业】
[java] view plaincopyprint?

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):【达内培训费用】
[java] view plaincopyprint?

try {
• InputStream stream = ClassLoader.getSystemResourceAsStream("fileinjar.txt"); BufferedReader in = new BufferedReader(new InputStreamReader(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):
[java] view plaincopyprint?

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(new InputStreamReader(url.openStream()));
• String str;
  while ((str = in.readLine()) != null) {
• System.out.println(str); }
• in.close();
  
• }
  
• } catch (IOException e) {
• }  

4,从URL中读取:【达内怎么样】
[java] view plaincopyprint?

try {
• 
  URL url = new URL("http://blog.csdn.net/kkdelta");
• System.out.println(url);
  
• BufferedReader in = new BufferedReader(new InputStreamReader(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):
[java] view plaincopyprint?

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(new InputStreamReader(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.原因是ClassLoader和Xclass.class.getClassLoader()是不同的,查找的路径不一样.