ORM IN WEB PROGRAMMING Course project report for 6WW Erik Wang

Problems with web programming

When people do the web design… Design from functional aspects Programmer also needs to understand database Code is not sophisticated

This keeps long from CGI, ASP, PHP, JSP… Traditional web programming has some problems

Low efficiency Hard to maintain Hard to re-use

Evolution of web system

Database layer DBMS

Business logic layer Functions Library

Present layer CGI

ASP

JSP

PHP

Data layer

Business Model Entity

Present layer Web

Application

Service

Business process

DBMS Data in memory

Data service

More abstract observation of business model Various data layer source and present method New database-like-system fit for large scale and fast data computing

ORM

ORM

Object relation mapping A Framework to do database – memory mapping “Free developers from database”

The idea from JAVA EE EJB – entity bean

May implementations – toplink, JPA, active record etc. Hibernate is an implementation of ORM which can be

used for Web Application

Data persistent

From the software designer’s view: You just know the data will be saved, but you don’t

need to worry who will do it and how they do it Data in memory is not persistent Data in database is persistent

From the programmer’s aspect – Call a persistent method without use SQL query

New method to thinking - MDE

Think about the object from the real world - Abstract things, using natural language to describe

them

- Business analyst and domain expert can describe requirements better

Hibernate

Everything Data

Approach by Hibernate

Hibernate provides a new method to design the system

1. Design the system from data aspect 2. Generate class from database entity 3. Use DAO to access data 4. Work with other frameworks

Using Hibernate

Direct engineering and Reverse engineering From JAVA code to database – generate DDL From database to JAVA code – generate JAVA CLASS

Relationship mapping define in XML or JAVA annotation 2 level of Cache

Case study – A news web system

Requirements statement A department news web site Publish news to the website - CRUD Highlight News has many reference objects: Image, reviews, related news, etc. Challenges Too many functions to be implemented Data relations are complex

Case study – Old idea of design

Consider from functional consideration Function 1: Login/Logout - login.php Function 2: Show a list – showallnews.php Function 3: Add a news – addnews.php … Database:

table – account table – news table – account_connect_news

If add a new entry: “A series of database queries are required”

Peter , Programmer

Case study - Access database

Access to database Use JDBC/ODBC Code in page $hostname_cnn1 = "localhost";

$database_cnn1 = "macmovie";

$username_cnn1 = "macmovie";

$password_cnn1 = "macmovie";

$cnn1 = mysql_pconnect($hostname_cnn1, $username_cnn1,$password_cnn1) or trigger_error(mysql_error(),E_USER_ERROR);

require_once('dbconn.php');

include 'util.php';

mysql_select_db($database_cnn1, $cnn1);

Peter , Programmer

No more SQL query

Case study – Abstract the problem

Abstract the factors in the problem Entity News, Images, Comments etc.. Properties SN, NAME, CONTENT, DATE…

Methods News can be: added, posted, audited, modified,

removed, etc.. Images can be: added, posted, audited, removed,

attached, etc...

Michal , Modeler

Case study - Relation Mapping

tdnews.xml <set name="Tdaddonimgs" cascade="all" table="tdnewsaddonimgs" > <key column="sn" /> <many-to-many column="isn" unique="true" class="eznews.Tdaddonimgs" /> </set> tdaddonimgs.xml <join table="tdnewsaddonimgs" optional="true" inverse="true"> <key column="isn" /> <many-to-one name="news" column="sn" not-null="true" /> </join>

Reverse Engineering Dave , DB guru

Peter , Programmer

Case study – Generate JAVA class

Peter , Programmer

Case study – Entity to database entity

Hibernate do database access works Includes:

Mapping data type to db type Generate entity JAVA class or DB DDL Translate JAVA methods to SQL queries

Hint:

Use connection pool work with Hibernate

Case study – example: add news

Get a news object and some image objects Add properties to news and image Refer image to the news Get a transaction object from session factory Call SaveorUpdate() What actually happen are: 1. Run a insert query into table news 2. Run some insert queries into table images 3. Run some insert queries into middle table news_image

Peter , Programmer

Case study - Following steps

Implement methods by JAVA programming Enclosure to a function Servlet Build web page – HTML/CSS/JS part Combine Servlet to web page (JSP) Use other JAVA solution to be better (Spring,

Structs)

Conclusions

ORM provides a new method to design software Advantages:

Re-use models from other system Web developers don’t need care about database

layer Improve the quality of the source codes

Disadvantage ORM is not a complete MDE implement Additional layer that increasing potential risk

(N+1 problem)

Thank you

Case study – Adopting MDE

Database design Consider from data flow aspect What kind of data will be composited What are the state changes for the objects Design the system from object aspect

Attributions? Functions?

N+1 problem from hibernate