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Middleware (2)

Nclab M.S.

Jinwon Lee

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Contents

CGI, Servlet, JSP

→

Client Session Management

JDBC (Java Database Connectivity)

Connection pooling

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Overview

ClientBrowser

Engine SupportingJSPs and Servlets Database

JDBC

ServletJSP,

Session

Connection Pooling

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Client Session Management

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Stateless HTTP Protocol

HTTP transaction is independent to each request.

Problems at Data Tracking, User Identification. Ex) website login, shopping cart.

Need to mange state information between transaction requests and Web Application

→ Session Tracking

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Session Tracking

Session TrackingManage states informationClient-side : CookieServer-side: HttpSession (Servlet API)

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CookiesA cookie is a piece of information that a site hands to your browser

The browser hands the site the cookie on each subsequent requestUnless the cookie is deleted, expired, modified..

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Servlet/JSP support CookiesJavax.serlvet.http package support Cookie class

Send to Client (HttpServletResponse class) Cookie myCookie = new Cookie(“key”, “value”)

// Create cookie and Set attribute response.addCookie(myCookie); // Send Cookie to Client(Cookie is part of the HTTP response header.)

Receive from Client(HttpServletRequest class) Cookie [] allCookie = request.getCookies(); // Receive allCookie from Client String value = myCookie[i].getValue(); // Find the specific one you are interested in

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Cookies don’t always taste good

Cookies can only contain small amounts

of data (all cookie data are strings)

Cookies might not be accepted by the browser

Cookies can get stale

→ Use Object in Server-side

(HttpSession)

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HttpSession

A session is a continuous connection from the same browser over a fixed period of time. Default is 30 minutes for Servlet Container To maintain session information, Use session

with browser cookies or encodeURL

Javax.servlet.http package support

HttpSession interface

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HttpSessionHow to obtain HttpSession objectHttpSession session = request.getSession(true); // read session id from cookie or encodeURL,and // if there are valid session object, return object. // else create new session with cookie

You can maintain a set of (key, value) paired information in the HttpSession object.

To store session-specific information, use the putValue(key, value) & getValue(key).

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encodeURL If the browser doesn’t accept cookies, session id

is appended to each URL in the HTML responseWhen the rewritten URL is accessed, the server extracts the appended session idString URL encodeURL(String URL); session id is append to URL and return URL [URL]  http://local/servlet/MyServlet?id=nannom [After encodeURL] http://local/servlet/MyServlet?id=nannom&JSevID= xxxxxxx

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Session Implemention

Informations of HTTP transaction are managed by using HttpSession

→ Security, efficiency

To track the HttpSession, it is the best way that user accept cookie

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JDBC

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JDBC

Application 개발시 Database system 과의 연동이 필수적 → JDBC (Java Database Connectivity)

JDBC API Java 로 작성된 Program 을 일반 Database 에 연결하기 위한 API 제공

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JDBC OverviewJDBC Overview

DB 와 User 사이에 Abstract Layer 제공 .

한가지 API 만을 이용하여 서로 상이한 DB 사용 가능 .

대부분의 DB Vendor 가 JDBC Spec. 에 따라 JDBC Driver 를 구현하여 제공 .

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Java Application

JDBC Driver Manager

(java.sql.*)

JDBC Driver

JDBC API

JDBC Driver API

DB

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JDBC DriverType I : JDBC-ODBC bridge plus ODBC driver

DataBase

JAVA 어플리케이션JAVA 어플리케이션

JDBC-ODBC BridgeJDBC-ODBC Bridge

기존의 ODBC 드라이버기존의 ODBC 드라이버

Native API( C/C++)Native API( C/C++)

DataBaseprotocol

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Type II : Native-API partly-Java driver

( JDBC 의 호출을 각 DB Client API 로 변환하여 호출 )

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Type III: JDBC-Net pure Java driver

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Type IV: Native-protocol pure Java driver

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장점JDBC 호출을 DBMS 의 고유한 Protocol 로

직접 변환해 처리하기 때문에 처리 속도가 가장 빠르다 .

Internet/Intranet 에 가장 적합한 방식

단점DB 고유의 Protocol 을 알고 있어야만 하므로

JDBC Driver Vendor 가 만들기에는 어렵고 주로 DBMS Vendor 에 의해 제공된다 .

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java.sql package JDBC 2.0 core API

Major interface Making a connection with a data source

DriverManager class Connection interface

Sending SQL statements to a database Statement interface

Retrieving and updating the results of a query ResultSet interface

Throwing exceptions SQLException

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Programming with JDBC API

1. DriverManager 에 해당 DBMS driver 등록Class.forName(String className );

“com.jk.jdbc.Driver”

2. 해당 Driver 로부터 Connection 객체 획득String jdbcURL="jdbc:jk:kmindb1@143.248.148.160:1433"; String user=“scott”; String passwd=“tiger”;

Connection conn=DriverManager.getConnection(jdbcURL, user, passwd);

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3. Connection 객체로부터 Statement 객체 획득

Statement stmt=conn.createStatement();

4. Statement method 를 이용하여 SQL 실행ResultSet rset=stmt.executeQuery(“SELECT id, name FRO

M emp”);

5. 결과를 ResultSet 으로 받아서 처리while(rset.next()) {

System.out.println(“ 사번 :” + rset.getInt(“id”));System.out.println(“ 이름 :” + rset.getString(“name”)); }

6. 종료rset.close(); stmt.close(); conn.close();

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Problems

Accessing the database can be slow

Lots of years and tears are spent optimizing database access

An obvious optimization is to reuse the JDBC connections

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References

BooksProfessional Java server programming

Websitehttp://java.sun.com/servlethttp://www.javanuri.net (servlet/jsp lecture 7 ~ 9)