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http学习笔记

2195113 — Thu, 28 Sep 2006 07:53:00 GMT

一.HTTP请求:
HTTP请求分为:
1).请求行
2).消息头
3).空行
4).正文

1.请求行
[方法 URI HTTP版本信息]
如: GET /index.htm HTTP/1.0

2.方法(全部大写):
GET      请求URI标识的资源
HEAD     请求获取响应消息头
PUT      请求存储资源,并用URI作为其标识
POST     请求服务器接收信息
CONNECT ?
TRACE
DELETE
OPTIONS

二.HTTP响应:
1).状态行
2).消息头
3).空行
4).正文(资源的内容,比如index.htm文件的文本内容)

1.状态行
HTTP版本信息状态码响应码描述
例: HTTP/1.1 200 OK

2.状态码(第一位表示响应的类别)
1xx:
2xx:
3xx:
4xx:
5xx:
HTTP协议状态码具体意义
   100 : Continue
   101 : witchingProtocols
   200 : OK
   201 : Created
   202 : Accepted
   203 : Non-AuthoritativeInformation
   204 : NoContent
   205 : ResetContent
   206 : PartialContent
   300 : MultipleChoices
   301 : MovedPermanently
   302 : Found
   303 : SeeOther
   304 : NotModified
   305 : UseProxy
   307 : TemporaryRedirect
   400 : BadRequest
   401 : Unauthorized
   402 : PaymentRequired
   403 : Forbidden
   404 : NotFound
   405 : MethodNotAllowed
   406 : NotAcceptable
   407 : ProxyAuthenticationRequired
   408 : RequestTime-out
   409 : Conflict
   410 : Gone
   411 : LengthRequired
   412 : PreconditionFailed
   413 : RequestEntityTooLarge
   414 : Request-URITooLarge
   415 : UnsupportedMediaType
   416 : Requestedrangenotsatisfiable
   417 : ExpectationFailed
   500 : InternalServerError
   501 : NotImplemented
   502 : BadGateway
   503 : ServiceUnavailable
   504 : GatewayTime-out
   505 : HTTPVersionnotsupported

三.HTTP消息头:
1. 普通
2. 请求头
3. 响应头
4. 实体头

格式:(名字大小写无关)
<名字>:<空格><值>

1.普通头
.Cache-Control (HTTP1.1, HTTP1.0:Pragma)
      缓存指令:
      请求时: no-cache,no-store,max-age,max-stale,min-fresh,only-if-cached
      响应时: public,private,no-cache,no-store,no-transform,must-revalidate,proxy-revalidate,max-age,s-maxage.
      例: Cache-Control: no-cache
.Date
      客户端:在发送正文时要包含Date,
      服务器:在响应时包含Date.
.Connection
.Pragma(1.0用)

2. 请求头
.Accept
.Accept-Charset
.Accept-Encoding
.Accept-Language
.Authorization
.Host(必须的)
.User-agent

3.响应头
.Location
.Server
.WWW-Authenticate,要包含在401中.

4.实体头
.Content-Encoding
.Content-Language
.Content-Length
.Content-Type
.Last-Modified
.Expires

2195113 2006-09-28 15:53 发表评论

关于ThreadLocal的使用

2195113 — Mon, 25 Sep 2006 08:18:00 GMT

1.线程中要使用的类.各线程只有其一个引用.

public class VarClass {

    private static ThreadLocal threadVar=new ThreadLocal(){
        protected synchronized Object initialValue(){
            System.out.println(Thread.currentThread().getName()+" initial value is 1");
            return new Integer(1);
        }};

    public int getValue(){
        return ((Integer)threadVar.get()).intValue();
    }

    public void setValue(){
        int a=getValue();
        a++;
        threadVar.set(new Integer(a));
    }
}

2.线程类

public class Worker extends Thread {
    private long interval=0;
    private boolean isRun=true;
    private VarClass v=null;

    public Worker(String name,VarClass v,long interval){
        setName(name);
        this.v=v;
        this.interval=interval;
    }

    public void run() {
        while(isRun){
            try{
                Thread.sleep(interval);
            }catch(InterruptedException e){
                e.printStackTrace();
            }
            v.setValue();
        }
        System.out.println(getName()+" is over at "+v.getValue());
    }

    public void stopThread(){
        isRun=false;
    }
}

3.测试类
public class TestThreadLocal {
   public static void main(String[] args){
       VarClass v=new VarClass();

       Worker w1=new Worker("Thread_A",v,100);
       Worker w2=new Worker("Thread_B",v,200);
       Worker w3=new Worker("Thread_C",v,300);
       Worker w4=new Worker("Thread_D",v,400);
       Worker w5=new Worker("Thread_E",v,500);

       w1.start();
       w2.start();
       w3.start();
       w4.start();
       w5.start();

       System.out.println("All threads is over after 20 seconds");

       //延时20秒后,终止5个线程
       try{
           Thread.sleep(20000);
       }catch(InterruptedException e){
           e.printStackTrace();
       }

       System.out.println("All threads will be overed");
       w1.stopThread();
       w2.stopThread();
       w3.stopThread();
       w4.stopThread();
       w5.stopThread();
}
}

4.测试结果:
All threads is over after 20 seconds
Thread_A initial value is 1
Thread_B initial value is 1
Thread_C initial value is 1
Thread_D initial value is 1
Thread_E initial value is 1
All threads will be overed
Thread_A is over at 200
Thread_B is over at 101
Thread_D is over at 51
Thread_C is over at 68
Thread_E is over at 42

5.结果说明:虽然各线程使用的是同一个对象的引用,但由于使用了ThreadLocal,实际上每个线程所操作的数据是不一样的.

2195113 2006-09-25 16:18 发表评论

Base64编码原理(随记)

2195113 — Thu, 21 Sep 2006 08:29:00 GMT

1. Base64使用A--Z,a--z,0--9,+,/ 这64个字符.
2. 编码原理:将3个字节转换成4个字节( (3 X 8) = 24 = (4 X 6) )
先读入3个字节,每读一个字节,左移8位,再右移四次,每次6位,这样就有4个字节了.
3. 解码原理:将4个字节转换成3个字节.
先读入4个6位(用或运算),每次左移6位,再右移3次,每次8位.这样就还原了.

2195113 2006-09-21 16:29 发表评论