Questions about cookies and sessions

Three objects ： client A, The server B, The server C

1. client A Request to server B, The server B Set up session data , For example, a user name is stored , The value is ：csdn

2. The server B Set the session After the data ,301 perhaps 302 Jump to server C

3. The server C Do nothing （ You can also do some business processing , Is not important ）,301 perhaps 302 Then jump to the server B

4. The problem is at this step , The server B here , Again from session Retrieve the user name stored before , The result is that , Output on the page as ：csdn

Normally, you can't get it .

adopt chrome Debug to see , step 1 in , Generate sessionid Store in client A, step 2 in , Jump to server C, Is not to bring sessionid Of , step 3 in , The server C Jump to server B, But with the steps 1 in , Produced sessionid

It's strange ,session It depends on cookie Of , step 1 Medium sessionid Store in client A, step 3 in , The server C Jump to server B, The server C This can also be seen as relative to the server B The client of , The server C There is no such thing as sessionid Of , But why did you bring it again sessionid Well ？