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Hibernate Case Study

Explore a case study on developing an enterprise system to sell kitchen worktop offcuts efficiently, using Hibernate ORM mapping and Agile methodologies. Phase 1 focuses on creating a JSP-based website with essential details.

clarencefrazier
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Hibernate Case Study

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  1. Hibernate Case Study Enterprise Applications Development & Integration Andrew Stratton

  2. Browser or App Business logic Database connection Presentation Database JSP Hibernate for Enterprise Java • Only a small part of a solution... • Often paired with Spring (framework) in Java • Example focuses on ASP based presentation, which could alternately be: • Application (i.e. WinForms) • XML/SOAP (i.e. Web Service) • WAP/WML (Mobile service) • Tier overview: User Java Hibernate

  3. Case Study : Kitchen Worktop offcuts • A large DIY retailer wishes to sell offcuts of kitchen worktops. Kitchen worktops typically come in three metre lengths. Most stores offer an in house cutting service, which can leave offcuts that the customer does not need or want. • The justification for the system is: • To reduce wasted warehouse space • To (potentially) allow reductions in costs for customer needing ‘just a couple more feet’ of worktop • For green credentials, i.e. to recycle/reduce waste • To increase income for the (charged for) cutting service • In order to accomplish this, an enterprise system is to be developed for use in house and (later) available externally as a web service

  4. Methodologies and Technologies • An Agile like approach is to be used, with sprints and incremental functionality • Test Driven Development is to be used, particularly for Web Services • JUnit is to be used for unit testing • Hibernate is to be used for ORM mapping

  5. Case Study : Phase 1 Detail • The first phase is to provide the following solution: • A JSP based web site for use in house, that display details of all offcuts available • These details to include: • Name: This is the short identifier for the type of worktop, e.g. ‘Shiny Light Grey Marble’. • Description : this is a free form area that records any extra details. • Length : in metric and imperial, typically up to 3m, down to 0.6m • Depth and Height : typically 60cm deep (default) and 2.5cm high • Contact details : free form, of the store and preferably person or role to speak with

  6. Case Study : Phase 1, Sprint 1 • The focus of this sprint is the presentation layer, supported by the minimum required business logic/data objects

  7. Presentation tier • Following a ‘front end first’ approach • N.B. We are first concentrating on the presentation tier and implementing whatever we need for the JSP to be complete • Create jspand html pages to allow you to: • enter a name for a worktop in a form • submit the form contents to a createWorktop.jsp page • e.g. you could call the page with http://localhost:8080/Worktops/createWorktop.jsp?name=Shiny%20Marble • An example page is: • <html> • <body> • Name entered is <%= request.getParameter("name")%> • </body> • </html> • Next add fields for Description, Length, Height, Depth • check the form submission and display of parameters

  8. Business Logic 1 • Next we add some business logic • Add a WorktopManager class, e.g. package com.worktops; publicclass WorktopManager { publicvoid createWorktop(String name, String description, String length, String height, String depth) { System.out.println("Request to create Worktop with" + "\nName=" + name + "\ndescription=" + description + "\nlength=" + length + "mm" + "\nheight=" + height + "mm" + "\ndepth=" + depth + "mm"); } }

  9. Business Logic 2 • Integrate this with the createWorktop.jsp, e.g. <jsp:useBean id="worktopManager" class="com.worktops.WorktopManager" /> <html> <body> Not much to say... <% worktopManager.createWorktop( request.getParameter("name"), request.getParameter("description"), request.getParameter("length"), request.getParameter("height"), request.getParameter("depth") ); %> </body> </html>

  10. Stop check • What have we gained? • + Separation of presentation from (business) logic / rules • + Business focused functionality (not yet implemented!) • - spaghetti? • - code dependencies • - run time incompatibilities (i.e. loss of compile time checking)

  11. Business Logic Implementation 1 • We need to separate out the Worktop POJO (Plain Old Java Object) from the manager - • Create Worktop class package com.worktops; import java.io.Serializable; public class Worktop { private String name; } • In the package explorer - right click name - Source -> Generate getters and setters...OK • Add the other properties: • description, length, height, depth • Generate getters and setters (use Ctrl-right click to select multiple properties) • Now we have a JavaBean...

  12. Business Logic Implementation 2 • Now we update the WorktopManager.createWorktop method, similar to: • And the jsp: • Run it again and check the output... publicvoid createWorktop(Worktop worktop) { System.out.println("Request to create Worktop with" + "\nName=" + worktop.getName() ..... <%@page import="com.worktops.Worktop"%> ... <% Worktop worktop = new Worktop(); worktop.setName(request.getParameter("name")); ... also set the other properties worktopManager.createWorktop(worktop); %>

  13. Stop Check • What have we gained? • + Separation of data object from (business) logic / rules • + Data focused class/objects • - more spaghetti? • - code dependencies • - Java beans do not impose compile time constructor checking

  14. Install Hibernate – at last • Download • Hibernate-3_2min.zip from blackboard • hsqldb.jar from blackboard (simple database – or use access) • Unzip hibernate to directory • e.g. F:\Hibernate3.2 • Copy hsqldb.jar into directory • e.g. F:\hsqldb • Create a new project ‘Worktops’ in Eclipse • Import all the jars in F:\Hibernate3.2\lib to WEB-INF/lib • import hsqldb.jar as well (or use access) • import F:\Hibernate3.2\hibernate3.jar as well • under build path choose add jar and pick all the lib jars

  15. Worktop class • Modify the Worktop class: ... import java.io.Serializable; public class Worktop implements Serializable { private Long id; // and add getter/setter ... • Note: Serializable makes the class able to be sent through a stream, e.g. file, http, ftp, etc., without using RMI. Hibernate uses it for storing ‘persistent’ copies of objects.

  16. Hibernate configuration file • This tells hibernate where to look for mapping files - this is a one off creation of file ‘hibernate.cfg.xml’ in the WEB-INF/src directory: • <?xml version='1.0' encoding='utf-8'?> • <!DOCTYPE hibernate-configuration PUBLIC • "-//Hibernate/Hibernate Configuration DTD 3.0//EN" • "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> • <hibernate-configuration> • <session-factory> • <property name="hibernate.connection.driver_class">org.hsqldb.jdbcDriver</property> • <property name="hibernate.connection.url">jdbc:hsqldb:data/test</property> • <property name="hibernate.connection.username">sa</property> • <property name="hibernate.connection.password"></property> • <property name="dialect">org.hibernate.dialect.HSQLDialect</property> • <property name="show_sql">true</property> • <property name="transaction.factory_class"> • org.hibernate.transaction.JDBCTransactionFactory • </property> • <property name="hibernate.cache.provider_class"> • org.hibernate.cache.HashtableCacheProvider • </property> • <property name="hibernate.hbm2ddl.auto">update</property> • <mapping resource="/com/worktops/worktop.hbm.xml"/> • </session-factory> • </hibernate-configuration>

  17. Adding a mapping file • Now we need a worktop.hbm.xml mapping file (in WEB-INF/src/com/worktops directory): • <?xml version="1.0"?> • <!DOCTYPE hibernate-mapping PUBLIC • "-//Hibernate/Hibernate Mapping DTD 3.0//EN" • "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> • <hibernate-mapping> • <class name="com.worktops.Worktop" table="worktops"> • <id name="id" column="id" type="long"> • <generator class="increment"/> • </id> • <property name="name" type="string"/> • <property name="description" type="string"/> • <property name="length" type="string"/> • <property name="height" type="string"/> • <property name="depth" type="string"/> • </class> • </hibernate-mapping>

  18. Logger configuration • While we’re at it, create the logger configuration file in log4j.properties in the WEB-INF/src directory: • log4j.rootCategory=INFO,A1 • log4j.appender.A1=org.apache.log4j.ConsoleAppender • log4j.appender.A1.layout=org.apache.log4j.PatternLayout • log4j.appender.A1.layout.ConversionPattern=%-5p- • Now update the jsp... Trying...<br> <% boolean success = false; try { Worktop worktop = new Worktop(); ... success = true; } catch (Exception e) { e.printStackTrace(); } if (success) { %> It worked!!! <% } else {%> Some problems.... <% } %>

  19. Updating Business Logic • The hibernate code needs to be added. • Amend the WorktopManager: • Now run it - and look in the console in eclipse for logging information: • Hibernate: select max(id) from worktops • Hibernate: insert into worktops (name, description, length, height, depth, id) values (?, ?, ?, ?, ?, ?) ... import org.hibernate.*; import org.hibernate.cfg.Configuration; ... publicvoid createWorktop(Worktop worktop) { SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); Session session = sessionFactory.openSession(); session.save(worktop); session.flush(); session.close(); System.out.println("Created Worktop with" + ...

  20. Checking the database contents • Now amend createWorktop.jsp: • and WorktopManager: It worked :- <br><br> <% java.util.List worktops = worktopManager.listWorktops(); for (int i = 0; i<worktops.size(); i++) { Worktop theWorktop = (Worktop) worktops.get(i); %> Worktop <%= theWorktop.getName() %>, Description: <%= theWorktop.getDescription() %> <br> <% } } else {%> private List listWorktops() { List result = null; SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); Session session = sessionFactory.openSession(); result = session.createQuery("from Worktop").list(); session.flush(); session.close(); return result; }

  21. Tutorial exercises • During the tutorial, follow the above example first, then: • Add (if you haven’t already) a form to enter new worktop details. N.B. The database is emptied EVERY time tomcat restarts (change to access if you wish to keep data). • Add a separate page (e.g. listWorktops.jsp) to display a list of worktops names only. • Add the ability to read a worktop - so when a user clicks on an entry in the list, the detail is shown. • Hint - use (Worktop) session.get(Worktop.class, id); • Add a form to update a worktop’s details by reading into a form, then updating the details. • hint - use session.merge(worktop) • Add the ability to delete a worktop entry - preferably with confirmation (use javascript); try session.delete(worktop);

  22. Where’s the benefit? • Consider: • How much Sql did you need to write? • Where do we need to change if (say) we only ‘mark’ worktops for deletion? (i.e. have a deleted flag) • What if we change the html? • What if we change the database contents? • What if we change database implementation (e.g. to Access)?

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