java常用类

}
/**
* 对 URL 参数据进行安全解码
* @param s
* @return
*/
public final static String decodeSafeRequestParameter(String s)
{
return new String(Base64.decode(s.getBytes()));
}
}

☆HTTP字符集编码过滤器

import javax.servlet.*;
import java.io.IOException;

/**
* 用于设置 HTTP 请求字符编码的过滤器，通过过滤器参数encoding指明使用何种字符编码,用于处理Html Form请求参数的中文问题
* @version 1.0
* @author 陶建风
*/
public class CharacterEncodingFilter
implements Filter
{
protected FilterConfig filterConfig = null;
protected String encoding = “”;

public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException
{
if(encoding != null)
servletRequest.setCharacterEncoding(encoding);
filterChain.doFilter(servletRequest, servletResponse);
}

public void destroy()
{
filterConfig = null;
encoding = null;
}

public void init(FilterConfig filterConfig) throws ServletException
{
this.filterConfig = filterConfig;
this.encoding = filterConfig.getInitParameter(“encoding”);

}
}

☆IO 操作的工具类

import java.io.*;
public final class StreamUtil
{
/**
* 将输入流复制到输出流
* @param is
* @param os
* @throws IOException
*/
public final static void write(InputStream is, OutputStream os) throws IOException
{
BufferedInputStream bis = new BufferedInputStream(is, 1024);
int c = bis.read();
while(c != -1)
{
os.write(c);
c = bis.read();
}
os.flush();
}

/**
* 将输入流按指定的编码转成字符串
* @param is
* @param encoding
* @return
* @throws IOException
*/
public final static String toString(InputStream is, String encoding) throws IOException
{
ByteArrayOutputStream bos = new ByteArrayOutputStream();
write(is, bos);
if(encoding == null) return new String(bos.toByteArray());
else return new String(bos.toByteArray(), encoding);

}

/**
* 将输入流按默认的编码转成字符串
* @param is
* @return
* @throws IOException
*/
public final static String toString(InputStream is) throws IOException
{
return toString(is, null);
}

/**
* 关闭输入流，忽略异常
* @param is
*/
public final static void closeQuitely(InputStream is)
{
try
{
if(is != null) is.close();
}
catch (IOException e)
{
}

}

/**
* 关闭输出流，忽略异常
* @param os
*/
public final static void closeQuitely(OutputStream os)
{
try
{
if(os != null) os.close();
}
catch (IOException e)
{
}
}

/**
* 半闭输入输出流，忽略异常
* @param is
* @param os
*/
public final static void closeQuitely(InputStream is, OutputStream os)
{
closeQuitely(is);
closeQuitely(os);
}
}

☆在JSP上实现类似ASP中的Global.asa 这样具有系统事件监听功能的程序并不难,我想这也是很多JSP朋友所关注的问题,那么本人就将实现过程展示如下:

1.实现监听类

package Bean.Sample;

import java.util.Date;
import java.servlet.http.HttpSessionEvent;
import java.servlet.http.HttpSessionListener;

public class counterListenerExam implements HttpSessionListener{

private static int count = 0;
private static int activeCount = 0;

public void sessionCreate(HttpSessionEvent evt){

long time = evt.getSession().getCreationTime();
System.out.println(“session 建立的时间” + new Date(time));

count ++;
activeCount ++;
}

public void sessionDestroyed(HttpSessionEvent evt){

activeCount —
}

public static String getCounteInfo(){

return “建立总数:” + count + ” ” +
“活动总数:” + activeCount;
}
}

2. 监听器的配置:

通过WEB应用程序的XML部署符WEB.XNL实现,在WEB.XML中添加一个元素,并嵌套元素(对应监听器的名称)

web.xml
…
.. Bean.Sample …

3. JSP页应用

<%@page import="Bean.Sample"%>
<% Sample.getCounterInfo(); %>