1. 1. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 1 Session: Pragmatic Architecture Java EE, latest brew Entity, Control and Boundary
2. 2. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 2 Objectives Learn about: Get an overview about the latest Java EE technologies used at the backend A warming up for the architectural aspects Get an idea about the ECB pattern as a general principle
3. 3. 3 Where are we right now? Existing architectures Architecture Patterns Customer & Business needs Further requirements Reference Architecture mining proven concepts vision analysis evolution triggering
4. 4. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 4 Some orientation Consumer Consumer Layer Integration Layer Business Process Layer Services Layer Component Layer OS Layer
5. 5. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 5 Module Java EE, latest brew
6. 6. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 6 The rise of Spring and Hibernate Spring Application framework Dependency Injection AOP support Non-invasiveness as a basic principle O/R persistence support for various frameworks Hibernate POJO based O/R persistence Spring and Hibernate became a popular alternative to J2EE development.
7. 7. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 7 Don't look back Until V5.0 Enterprise Java really had a bad reputation: Too complex, especially when it comes to EJBs (Home Interface, Local Interface, Remote Interface, Bean class, Deployment Descriptor) Too inflexible, especially when it comes to CMP (heavy-weighted objects, Session Facades and Value Objects) Outdated, especially when it comes to AOP and DI Too expensive, especially when it comes to app-servers Too ... But things change!
8. 8. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 8 Right now Java EE V5.0 (and higher) has a lot to provide: Context and Dependency Injection (CDI) Validators JPA 2.x Convention over Configuration And its a standard supported by various vendors
9. 9. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 9 Convention over Configuration A principle borrowed from the Ruby on Rails tribe Decreases the number of decisions to be made and configurations to be done by default configurations Annotations replace XDoclet's JavaDoc tags: Compiler checks Type safety (instead if just strings) All information previously stored in the deployment descriptor file (the meta-data hell) now moved into annotations (but DD file still optional and overwrites Annotation)
10. 10. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 10 XDoclet & Annotations XDoclet: Annotation: /** * @ejb.bean name = UserMgmtService view-type = remote */ public class UserMgmtService implements SessionBean { } @Stateless @Remote(UsrMgmt.class) public class UserMgmtService implements UsrMgmt { }
11. 11. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 11 Annotations @Stateless: Marks the class as a Stateless Session Bean, no need to implement an interface or to extend a class Provides a default transaction handling (every method will be executed in a single transaction) @LocalBean All public methods will be exposed to local clients, no need to implement a dedicated interface Local clients - like Servlets or other EJBs might obtain a reference by means of dependecy injection.
12. 12. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 12 Lab Implement Stateless Session Bean (not more than 15 min.)
13. 13. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 13 Dependency injection Providing an external dependency (any ressource like another EJB, a DataSource, a JMS destination ) to a software component. Previously (within a client bean) public void init() { try { ctx = new InitialContext(); facade = (UserManagementService) ctx.lookup("ejb/facade/UserManagementService"); } catch (NamingException e) { e.printStackTrace(); } }
14. 14. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 14 Dependency Injection In our days: No Exception handling, no casting issues, no misspelling, no deployment descriptors, no ... @Stateless @Remote(Client.class) public class ClientBean implements Client { @EJB private UserMgmtLocal userMgmt; ... }
15. 15. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 15 Lab Implement Dependency Injection (not more than 15 min.)
16. 16. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 16 Bean Validation JSR 303: Bean Validation you can use it anywhere you like: front-end, back-end, even DTO (if you follow this pattern) reference implementation is Hibernate Validator v4.x validation on two different levels: attribute or entire bean i18n ready and message are parameterized extensible with your own validators configurable with annotations or XML
17. 17. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 17 Several build-in Validators Quite a few Validators are already implemented within the javax.validator package, some examples: @AssertFalse / @AssertTrue The value of the field or property must be false / true @Max / @Min The value of the field or property must be an integer value lower / higher than or equal to the number in the value element. @NotNull The value of the field must not be null @Past / @Future The date has to be in the past / future ... @see link below
18. 18. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 18 Example Considering a user, we might want to ensure the following: public class User implements Serializable { @NotNull private long id; @NotNull @Size(min = 4, max = 8) private String user; @NotNull @Size(min = 8, max = 15) private String password;
19. 19. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 19 Example: evaluating If not done by the container (which is the usual case), we can evaluate 'manually' public void testValidation() { Set> violations = validator.validate(user); System.out.println("Number of violations: " + violations.size()); for (ConstraintViolation constraintViolation : violations) { System.out.println(constraintViolation.getPropertyPath() + " " + constraintViolation.getMessage()); } } @BeforeClass public static void init() { user = new User(); user.setPassword("abcdef"); factory = Validation.buildDefaultValidatorFactory(); validator = factory.getValidator(); }
20. 20. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 20 Writing your own validator not covered if this training! Though the JSR defines a whole bunch of standard constraint annotations such as @NotNull, @Size, @Min or @AssertTrue, there will always be validation requirements, for which these standard annotations won't suffice. Being aware of that problem, the specification authors laid out the API in an expansible manner, that allows users to define their custom constraint annotations. A nice tutorial can be found here: http://musingsofaprogrammingaddict.blogspot.de/2009/02/getting-started-with- jsr-303-bean.html
21. 21. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 21 Lab Implement Validator (not more than 15 min.)
22. 22. 22 AOP / Interceptors Aspect-oriented programming A paradigm more than a pattern. Certain software properties cannot be isolated in single functional unit, instead they crosscut multiple components Such cross-cutting concerns result in tangled code that is hard to develop and maintain, e.g.: Logging Authentication
23. 23. 23 Interceptor Non UML: EJB Container Interceptor(s) Request Response
24. 24. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 24 Interceptors Introduced with EJB 3.0 Are one of the Java EE pendant to Aspects (the other is a Servlet Filter). Are pretty easy to implement
25. 25. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 25 Interceptors Provided EJBs with a rudimentary Aspect Oriented Programming system. Enable a clean distinction of business logic and meta or support code. Are classes (distinct form the beans themself). Interpose themselves on methods calls or life cycle events. Have access to information about the business method that triggered it, including method names an parameters. Can halt processing of the business method. Can be used on session and message-driven beans. A bean can have any number of Interceptors. Common uses for interceptors are security checking, logging or auditing functions. separation of concerns
26. 26. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 26 An Interceptor public class PerformanceInterceptor { private Logger log = Logger.getLogger(this.getClass().getName()); @AroundInvoke public Object onMethodCall(InvocationContext ctx) throws Exception { log.info(">>> Entering interceptor"); long start = System.currentTimeMillis(); log.info("Invocation of: " + ctx.getMethod().getName()); try { // go ahead using the invocation context return ctx.proceed(); } finally { long end = System.currentTimeMillis(); long duration = end - start; log.info("Duration of invocation: " + duration); } } }
27. 27. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 27 Intercepting @Stateless(mappedName = "ejb/facade/UserManagementService") @Remote(UserManagementService.class) // alternatively you can use the interceptor here as well public class UserManagementServiceBean implements UserManagementService { // use interceptor (comment if using ejb-jar.xml) @Interceptors(PerformanceInterceptor.class) public User findUserByCredentials(String user, String pwd) { User u = new User("peterp", "neverland"); return u; } public User createUser(User u) { return u; } } Annotate method(s) or class
28. 28. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 28 Configuration by XML The recommened way as we can change without recompilation UserManagementServiceBean de.brockhaus.userMgmt.backend.util.PerformanceInterceptor findUserByCredentialsjava.lang.Stringjava.lang.String
29. 29. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 29 Lab Implement Interceptor (not more than 15 min.)
30. 30. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 30 Persistent Entities / JPA 2.x JPA defines a way to map regular, plain old Java objects (POJOs) to a database. These plain Java objects are called persistent entities (and no longer EntityBeans): they can be used in regular Java applications outside of an application server and can even be used to transfer data between a client and a server. In EJB 2.1 specification, entity beans were heavyweight: dependent on the application server. dependent on the entire Java EE runtime environment. cause high memory consumption.
31. 31. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 31 Parts of JPA The JPA Specification consists of three parts: Entities business objects. persisted in the database. Persistence unit A group of a finite set of Entity bean classes. Associated to a particular database so that the persistence provider knows where, how, and with what kind of database it is interacting. Are defined in an xml deployment descriptor named persistence.xml. EntityManager The EntityManager provides an API to maintain the Entities. provides the persistence context for a particular persistence unit.
32. 32. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 32 Basic Mappings The entity: @Entity Defines the class as persistent Entity The Table: @Table By default tablename == classname You can change this (veeeery needful in case of reserved word like USER) by @Table(name=TABLENAME) You can define unique constraints: The primary key: @Id you need to have one but can leave generation to the provider, we'll see later @Table( uniqueConstraints=@UniqueConstraint( columnNames={"FIRSTNAME", "LASTNAME"}) )
33. 33. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 33 Basic Mappings The attributes/fields: @Column Defines a lot of switches like: name=TABLE_NAME if the field identifier is not appropriate or whatsoever. unique=true (default is false), insertable/updateable=false (default is true) table=OTHER_TABLE, default is (same table) length=8 (default is 255) precision=2, column decimal precision (default is 0) scale=1, column decimal scale if useful (default is 0)
34. 34. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 34 Example @Entity public class User implements Serializable { private static final long serialVersionUID = 4616273573516105734L; @Id @GeneratedValue(strategy = GenerationType.AUTO) private long id; @NotNull @Size(min = 4, max = 8) @Column(unique = true) private String user; @NotNull @Size(min = 8) private String password; @ManyToOne(cascade={CascadeType.ALL}) private Person person; public User() { } public Person getPerson() { return person; }
35. 35. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 35 The EntityManager A service provided by JPA, all access to an entity goes through this service. Provides a query API and life cycle methods for the entity. To interact with entity beans, just plain Java is needed. Entity beans and EntityManager do not require an application server to be used. You can use Java persistence in unit tests and standalone Java applications like any Java library. Two options for clients to use the EntityManager: container managed, container runtime is responsible for providing and determining the EntityManager for applications. application managed, the application is responsible for the EntityManager itself.
36. 36. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 36 Application-managed EntityManager In Java SE applications you must use an EntityManagerFactory. How to get the EntityManagerFactory in Java SE: EntityManagerFactory factory; factory = Persistence.createEntityManagerFactory(persistence-unit-name); EntityManager manager = factory.createEntityManager(); ... // do some work with the EntityManager ... // close factory and releasing any resources that it holds factory.close();
37. 37. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 37 Container-managed EntityManager Only available within an application server. The container injects the EntityManager, once Annotation @PersistenceContext is used. unitName is the name of the persistence-unit which will be used. (optional) type can set to EXTENDED in stateful SessionBeans, default is TRANSACTION-SCOPED. Alternatively the JNDI lookup can be used. //use the field injection @PersistenceContext(unitName=persistence-unit-name) private EntityManager objEntityManager; //alternatively the injection can be used on the setter @PersistenceContext(unitName=persistence-unit-name) public void setFactory(EntityManager f){ this.objEntityManager = f; } // or use SessionContext lookup method EntityManager objEntityManager = (EntityManager)ctx.lookup(java:comp/env/persistence-unit-name)
38. 38. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 38 In search for definitions Persistence Unit A persistence unit defines a set of all entity classes that are managed by EntityManager instances in an application. This set of entity classes represents the data contained within a single data store. Persistence units are defined by the persistence.xml configuration file. The JAR file or directory whose META-INF directory contains persistence.xml is called the root of the persistence unit. The scope of the persistence unit is determined by the persistence units root. Each persistence unit must be identified with a name that is unique to the persistence units scope.
39. 39. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 39 In search for definitions PersistenceContext A persistence context is a set of managed entity instances that exist in a particular data store. The EntityManager interface defines the methods that are used to interact with the persistence context.
40. 40. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 40 Deployment Descriptor Condensed and simple: The JPA specification requires a simple XML deployment descriptor. The deployment descriptor is called persistence.xml and is placed in the META-INF directory. (which has to be on the classpath in case of JavaSE) the persistence.xml configures basic things like: name of the persistence unit service. the used datasource / database defines where to look for entity beans. mandatory
41. 41. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 41 org.hibernate.ejb.HibernatePersistencede.brockhaus.userMgmt.backend.Userde.brockhaus.userMgmt.backend.Person Example: persistence.xml (JavaSE) mandatory
42. 42. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 42 The EntityManager Class Three kinds of operations: Entity live cycle management persist() a new instance is managed and persistent. remove() destroy entities data in the database. merge() merge the state of the given entity into the current persistence context. Database synchronisation operations flush() synchronize the persistence context. refresh() refreshes the instance from database.
43. 43. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 43 The EntityManager Class Three kinds of operations: Entity lookup and queries find() find by primary key and initialize the state based on the lazy-loading policies of each property. getReference() get an instance, whose state may be lazily fetched. createQuery() locate persistence object by using JP-QL.
44. 44. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 44 Example of using the Entity Manager @Stateless(mappedName = "ejb/facade/UserManagementService") @Remote(UserManagementService.class) public class UserManagementServiceBean implements UserManagementService { private EntityManager em; public UserManagementServiceBean() { this.em = EntityManagerHelper.getEntityManager(); } public User createUser(User u) { EntityTransaction tx = em.getTransaction(); try { tx.begin(); em.persist(u); tx.commit(); } catch(Exception e) { e.printStackTrace(); tx.rollback(); } return u; }
45. 45. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 45 Queries and JPQL Language to define queries for finder and select methods. compiled to the target language. is similar to SQL The query references the abstract schema name of a bean as its model, defined as the classname of the entitiy (default mapping) or overwritten with the @table annotation on class level. Used to define the query methods. Finder methods Select Methods In the JP-QL has four clauses: - Select clause Optional From clause Optional Where clause Optional Order By clause
46. 46. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 46 Named Queries Are a type of static queries. Define in the code or overwritten with deployment descriptor (can be changed by administrator or deployer then) @Entity @NamedQueries({ @NamedQuery(name = "User.findByCredentials", query = " FROM User AS u WHERE u.user = :user AND password = :pwd" ) } ) public class User implements Serializable { private static final long serialVersionUID = 4616273573516105734L; @Id @GeneratedValue(strategy = GenerationType.AUTO) private long id;
47. 47. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 47 Invocation Implements at respective service Make use of TypedQuery (EJB 3.1 only) public User findUserByCredentials(String user, String pwd) { TypedQuery tQuery = em.createNamedQuery("User.findUserByCredentials", User.class); tQuery.setParameter("user", user); tQuery.setParameter("pwd", pwd); return tQuery.getSingleResult(); }
48. 48. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 48 Lab Implement JPA (not more than 15 min.)
49. 49. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 49 Module Entity, Control and Boundary
50. 50. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 50 The dozens of technologies but no concise guideline to structure these To provide an (functional) example: The ISA 95 international standard for developing an automated interface between enterprise and control systems. This standard has been developed for global manufacturers. It was developed to be applied in all industries, and in all sorts of processes, like batch processes, continuous and repetitive processes.
51. 51. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 51 ISA 95 The activity model of ISA 95 How to apply the technologies? Guess you can easily find similar in your domain Detailed Scheduling Resource Management Tracking Dispatching Definition Management Data Collection Execution Analysis
52. 52. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 52 Cohesion From wikipedia The measure how strongly related and focused the the various responsibilities of a software module are. Modules with high cohesion tend to be preferrable as high cohesion is associated with various benefits like robustness, reliability and reusability. In Java EE Main responsibility of a business component is the exposure of it's specifications or contract and hiding it's realization
53. 53. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 53 ECB Pattern (get the things sorted) Entity Control Boundary Based upon Robustness Diagrams (http://www.agilemodeling.com/artifacts/robustnessDiagram.htm) Boundary: user interface Control: actual process or activity Entity: a concept from an enterprise context. Elements are generic enough to be mapped either to service- oriented or object-oriented architectures. Boundary Control Entity Adam Bien
54. 54. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 54 ECB Pattern in JavaEE Boundary: Service Faade or Gateway, exposes functionality of a component by means of several protocols and technologies Control: reusable, fine-grained service behind a boundary might be optional or generic in simple use cases such as CRUD or MDM (master data management) Entity: object-oriented or procedural domain objects. In most cases mapped to a single JPA entity
55. 55. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 55 Mapping ECB to Java Business components Can be mapped directly to Java packages, e.g. de.brockhaus.userMgmt Boundary, control and entity can be mapped to subpackages within the business component package: de.brockhaus.userMgmt.boundary de.brockhaus.userMgmt.control de.brockhaus.userMgmt.entity The whole business component might be realized as an individual jar Interfaces and exchange objects might be put into a dedicated services archive (although we don't do during this training)
56. 56. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 56 Common Interfaces, Business Objects, Exceptions Architectural blueprint Boundary Control Entity
57. 57. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 57 ECB as a general guideline Fits nicely into the reference architecture as we can model every activity within the activity model as ECB component Still there are a lot of Design Patterns which might be applied to improve the design.
58. 58. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 58 Boundary Control Entity DAO & Domain Store Generic DAO Singleton Service Starter Dual View SOA Facade Lightweight asynchronous Facade Multichannel Facade TO & DTO Paginator Bean Locator Multichannel Facade Resource Binder Payload Extractor Aynchronous Resource Integrator Infrastructure Patterns related to ECB Pattern
59. 59. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 59 Lab Implement ECB Pattern (not more than 15 min.)
60. 60. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 60 Review Session Review: What is the ECB pattern good for?
61. 61. Copyright by Brockhaus GmbH, alle Rechte reserviert, unautorisierte Vervielfltigung untersagt 61 Recommeded reading http://java.sun.com/blueprints/corej2eepatterns/ http://www.corej2eepatterns.com/Patterns2ndEd/ Adam Bien, J2EE Patterns, Addison Wesley 2002, ISBN: 3-8273-1903-X Floyd Marinescu, Ed Roman: Ejb Design Patterns: Advanced Patterns, Processes, and Idioms; Wiley & Sons, ISBN-10: 0471208310 And other ... Photo: Bundesarchiv