ServletContext读取资源的三种方式

package cn.csdn.web.servlet;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.util.Iterator;
import java.util.Properties;
import java.util.Set;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Demo02Servlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
/*获取ServletContext对象*/
ServletContext context = this.getServletContext();
URL url = context.getResource("WEB-INF/classes/db.properties");
InputStream is = url.openStream();
/*解析properties的文件*/
Properties prop = new Properties();
//从输入流中读取属性列表（键和元素对）。
prop.load(is);
Set<String> set = prop.stringPropertyNames();
//遍历set集合
Iterator<String> it = set.iterator();
while(it.hasNext()){
String key = it.next();
String value = prop.getProperty(key);
System.out.println(key+"-----"+value);
}

response.getWriter().print("ha");


}

public void prop(HttpServletResponse response)
throws FileNotFoundException, IOException {
/*获取ServletContext对象*/
ServletContext context = this.getServletContext();
/*读取db.properties文件*/
String path =context.getRealPath("WEB-INF/classes/db.properties");
/*根据文件的路径 构建文件对象*/
File file = new File(path);
/*根据file文件对象 创建输入流*/
InputStream is = new FileInputStream(file);
/*解析properties的文件*/
Properties prop = new Properties();
//从输入流中读取属性列表（键和元素对）。
prop.load(is);
Set<String> set = prop.stringPropertyNames();
//遍历set集合
Iterator<String> it = set.iterator();
while(it.hasNext()){
String key = it.next();
String value = prop.getProperty(key);
System.out.println(key+"-----"+value);
}

response.getWriter().print("haha");
}

public void test1(HttpServletResponse response, ServletContext context)
throws IOException {
/*第一步：读取资源的位置*/
//绝对路径
/*File file = new File("D:\\NCode\\myeclipse\\workspace\\20111019\\src\\res\\a.jpg");
InputStream is = new FileInputStream(file);*/
//第一种方式读取外部的资源文件
InputStream is = context.getResourceAsStream("/WEB-INF/classes/res/a.jpg");
// response.getWriter().write("realPath==="+realPath);
response.setHeader("Content-Type", "image/jpeg");

OutputStream os = response.getOutputStream();

byte buffer[] = new byte[1024];
int len=0;
while( (len=is.read(buffer))!=-1){
os.write(buffer, 0, len);
}
os.close();
is.close();
}
public void test2(HttpServletResponse response, ServletContext context)
throws IOException {
/*第一步：读取资源的位置*/
//绝对路径
/*File file = new File("D:\\NCode\\myeclipse\\workspace\\20111019\\src\\res\\a.jpg");
InputStream is = new FileInputStream(file);*/
//第一种方式读取外部的资源文件
InputStream is = context.getResourceAsStream("/images/a.jpg");
// response.getWriter().write("realPath==="+realPath);
response.setHeader("Content-Type", "image/jpeg");

OutputStream os = response.getOutputStream();

byte buffer[] = new byte[1024];
int len=0;
while( (len=is.read(buffer))!=-1){
os.write(buffer, 0, len);
}
os.close();
is.close();
}

}