401-09.md

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page	401.09 Reading Notes	/401-R09/

Java's Web Request Response Cycle

WRRC Overview

1. Local processing
2. DNS Request (for IP address)
3. TCP Connection (to ensure packet order)
4. HTTP Request (request line, header, & body)
5. Finish & Acknowledgement packets (both directions)

Java's WRRC

• Java uses the HttpClient class and contained methods for web requests and responses (formerly used HttpUrlConnection class)

• HttpUrlConnection

  • Pros: No library imports required;

  • Cons: Limited functionality compared to other libraries; Many deprecated features;

  • Common request-related methods: openConnection() to create instance (of object, not connection itself); .setRequestMethod() with the argument being the desired request (GET, DELETE, TRACE, etc); getHeaderField() for reading headers from the calling connection; setConnectTimeout() (in milliseconds); HttpCookie.parse()

• HttpClient

  • Pros: multiple threads in req/res; easier to maintain; optional asynchronicity;

  • Common request-related methods: .header()/.headers() (depending on if using one pair per or multiple pairs of key-values); timeout() (with #, then units as args); .newBuilder() to create a new builder instance which has many related methods;