几个小servlet程序

1.读写

//设置服务器的响应内容类型，从文件中读取内容

response.setContentType("text/html");
response.setCharacterEncoding("gb2312");
PrintWriter out = response.getWriter();
String fileName = "content.txt";
String realPath = new File(realPath);

//取得文件绝对路径
File file = new File(realPath);

if(file.exists()){
FileReader reader = new FileReader(file);
BufferedReader bufferReader = new BufferedReader(reader);
String line = null;

//读取文件内容
while((line = bufferReader.readLine())!=null){
out.print(""+line+"
");

}else
{
out.print("文件不存在");
}
}

//设置服务器的响应内容类型，并创建一个文件
response.setCharacterEncoding("gb2312");
PrintWriter out = response.getWriter();
String fileName = "new.txt";

String realPath = request.getRealPath(fileName);
File file = new File(realPath);
FileWriter writer = new FileWriter(file);

//在文件中写入内容
BufferedWriter bufferWriter = new BufferedWriter(writer);
bufferWriter.write("计算机网络");
bufferWriter.newLine();
bufferWriter.write("计算机组成原理");
bufferWriter.flush();
bufferWriter.close();
writer.close();

2.取出http的头部内容，并在页面打印

response.setContentType("text/html");

PrintWriter out = response.getHeader(name);

//首先使用方法取出http头信息的名称，然后循环取出对应的头信息的值

Enumeration e =request.getHeaderNames();

while(e.hasMoreElements()){

String name = (String)e.nextElement();

String value = request.getHeader(name);

out.println(name+"="+value+"
");

}