loadrss.java

《精通AJAX》光盘 要求： JDK1.4.2 以上版本 数据库采用MySQL 4.1.4 以上版本 服务器采用Tomcat 5 以上版本 开发工具采用Eclipse 3.0

package book.rssreader;

import java.io.*;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Date;

public class LoadRSS {
	protected String cacheDirName = "";// 保存缓存的目录名

	protected long cacheTime = 0;// 缓存时间

	protected boolean bCache = true;// 是否要在缓存中读取数据

	String fileName = "";// 保存在缓存中的文件名

	public String getRSS(String url) {
		// 首先设置文件名
		if (url == null || url.equals(""))
			return "";
		else
			fileName = url.substring(url.lastIndexOf("/") + 1);
		StringBuffer bf = new StringBuffer();

		if (cacheDirName == null || cacheDirName.equals(""))// 如果没有设置缓存目录，则不需要在缓存中读
			bCache = false;
		if (bCache) {// 如果在缓存中度数据
			File cacheFile = new File("C:\\" + cacheDirName, fileName);// 查找C盘下给文件
			if (!cacheFile.exists()) {// 如果该文件不存在，则新建目录
				bCache = false;
				try {
					cacheFile.createNewFile();
				} catch (IOException e) {
					e.printStackTrace();
				}
			} else {
				long interval = new Date().getTime() - cacheFile.lastModified();// 比较该文件与缓存的时间
				if (interval >= cacheTime)// 如果大于或等于缓存时间，则不在缓存中读取
					bCache = false;
			}
		}
		if (bCache) {// 如果从缓存中读取
			bf.append(readFromCache(url));
		} else {// 如果不从缓存中读取
			bf.append(readNew(url));
		}
		return bf.toString();
	}

	// 该方法读出文件的内容
	public String readFromCache(String url) {
		StringBuffer buffer = new StringBuffer();
		File cacheFile = new File("C:\\" + cacheDirName, fileName);
		try {
			BufferedReader in = new BufferedReader(new FileReader(cacheFile));
			String line;
			while ((line = in.readLine()) != null) {
				buffer.append(line);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		return buffer.toString();

	}

	public String readNew(String url) {
		StringBuffer buffer = new StringBuffer();
		try {
			URL u = new URL(url);// 定义URL对象
			BufferedReader in = new BufferedReader(new InputStreamReader(u
					.openStream()));// 获得URL对象的所输出的数据
			String inputLine;
			while ((inputLine = in.readLine()) != null) {
				buffer.append(inputLine);
			}
			in.close();
			writeNew(url, buffer.toString());// 些到文件中
		} catch (MalformedURLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return buffer.toString();
	}

	public void writeNew(String url, String content) {
		File cacheFile = new File("C:\\" + cacheDirName, fileName);
		try {
			if (!cacheFile.exists())
				cacheFile.createNewFile();
			FileOutputStream out = new FileOutputStream(cacheFile);
			byte[] b = content.getBytes();
			out.write(b);
			out.flush();
		} catch (IOException e) {
			e.printStackTrace();
		}

	}

	public boolean isBCache() {
		return bCache;
	}

	public void setBCache(boolean cache) {
		bCache = cache;
	}

	public String getCacheDirName() {
		return cacheDirName;
	}

	public void setCacheDirName(String cacheDirName) {
		this.cacheDirName = cacheDirName;
	}

	public long getCacheTime() {
		return cacheTime;
	}

	public void setCacheTime(long cacheTime) {
		this.cacheTime = cacheTime;
	}

}