Advanced Web Systems 9- Hibernate annotations, Spring integration, Aspect Oriented Programming. A. Venturini

Transcription

1 Advanced Web Systems 9- Hibernate annotations, Spring integration, Aspect Oriented Programming A. Venturini

2 Contents Hibernate Core Classes Hibernate and Annotations Data Access Layer with Spring Aspect Oriented Programming

3 Hibernate Overall Structure

4 Hibernate Architecture

5 Hibernate Core Concepts: SessionFactory Session Factory Threadsafe is a cache of compiled mappings for a single database. used to retrieve Hibernate Sessions Optional second level cache

6 Session Session A single-threaded, short-lived object Temporary bridge between the app and the data storage Provides CRUD operations on Objects Wraps a JDBC Connection / J2EE Data Source Serves as a first level object cache, used when navigating the object graph or looking up objects by identifier

7 Persistent Objects and Collections Short-lived, single threaded objects containing persistent state and business function. These can be ordinary JavaBeans/POJOs They are associated with exactly one Session Once the Session is closed, they will be detached and free to use in any application layer (for example, directly as data transfer objects to and from presentation)

8 Transient and detached objects and collections Instances of persistent classes that are not currently associated with a Session. They may have been instantiated by the application and not yet persisted, or they may have been instantiated by a closed Session.

9 Transaction TransactionFactory. A factory for Transaction instances. It is not exposed to the application, but it can be extended and/or implemented by the developer. Transaction. A single-threaded, short-lived object used by the application to specify atomic units of work. It abstracts the application from the underlying JDBC, JTA or CORBA transaction.

10 Instance State Transient. The instance is not associated with any persistence context. It has no persistent identity or primary key value. Persistent. The instance is currently associated with a persistence context. It has a persistent identity (primary key value) and can have a corresponding row in the database. Detached. The instance was once associated with a persistence context, but that context was closed, or the instance was serialized to another process. It has a persistent identity and can have a corresponding row in the database.

11 Working with Persistent Objects Session session = null; Transaction tx = null; try { session = factory.opensession(); tx = session.begintransaction(); session.delete(address); tx.commit(); } finally { } session.close(); Start a Session Transaction is started The object is deleted The transaction is committed The session is closed

12 Hibernate.cfg.xml <hibernate-configuration> <session-factory> <property name="hibernate.connection.datasource">java:comp/env/jdbc/hsql</property> <property name="hibernate.dialect">org.hibernate.dialect.hsqldialect</property> <property name="hibernate.current_session_context_class">thread</property> <property name="hibernate.transaction_factory_class">org.hibernate.transaction.jdbct ransactionfactory</property> <!-- SQL to console logging --> <property name="show_sql">true</property> <property name="format_sql">true</property> <property name="use_sql_comments">true</property> <!--Hibernate mapping files --> <mapping resource="pizza/domain/pizzaorder.hbm.xml" /> <mapping resource="pizza/domain/systime.hbm.xml" /> <mapping resource="pizza/domain/pizzasize.hbm.xml" /> <mapping resource="pizza/domain/topping.hbm.xml" /> </session-factory> </hibernate-configuration>

13 Sample Mapping file <hibernate-mapping> <class name="pizza.domain.topping" table="topping"> <id name="id" type="int"> <column name="id" /> <generator class="native" /> </id> <property name="toppingname" type="string"> <column name="topping_name" length="30" not-null="true" unique="true" /> </property> <set name="pizzaorders" inverse="true" table="order_topping"> <key> <column name="topping_id" not-null="true" /> </key> <many-to-many entity-name="pizza.domain.pizzaorder"> <column name="order_id" not-null="true" /> </many-to-many> </set> </class> </hibernate-mapping>

14 create table Person ( personid bigint not null primary key, addressid bigint not null ) create table Address ( addressid bigint not null primary key ) Collection Mappings: many to one class name="person"> <id name="id" column="personid"> <generator class="native"/> </id> <many-to-one name="address" column="addressid" not-null="true"/> </class> <class name="address"> <id name="id" column="addressid"> <generator class="native"/> </id> </class> create table Person ( personid bigint not null primary key, addressid bigint not null ) create table Address ( addressid bigint not null primary key )

15 create table Person ( personid bigint not null primary key, addressid bigint not null ) create table Address ( addressid bigint not null primary key ) Collection Mappings: one to one <class name="person"> <id name="id" column="personid"> <generator class="native"/> </id> <many-to-one name="address" column="addressid" unique="true" not-null="true"/> </class> <class name="address"> <id name="id" column="addressid"> <generator class="native"/> </id> </class> create table Person ( personid bigint not null primary key, addressid bigint not null unique ) create table Address ( addressid bigint not null primary key )

16 create table Person ( personid bigint not null primary key, addressid bigint not null ) create table Address ( addressid bigint not null primary key ) Collection Mappings: : many to many <class name="person"> <id name="id" column="personid"> <generator class="native"/> </id> <set name="addresses" table="personaddress"> <key column="personid"/> <many-to-many column="addressid" class="address"/> </set> </class> <class name="address"> <id name="id" column="addressid"> <generator class="native"/> </id> </class> create table Person ( personid bigint not null primary key ) create table PersonAddress ( personid bigint not null, addressid bigint not null, primary key (personid, addressid) ) create table Address ( addressid bigint not null primary key )

17 Bidirectional association: one to many/ many to one <class name="person"> <id name="id" column="personid"> <generator class="native"/> </id> <many-to-one name="address" column="addressid" not-null="true"/> </class> <class name="address"> <id name="id" column="addressid"> <generator class="native"/> </id> <set name="people" inverse="true"> <key column="addressid"/> <one-to-many class="person"/> </set> </class> create table Person ( personid bigint not null primary key, addressid bigint not null ) create table Address ( addressid bigint not null primary key )

18 Mapping with annotation Instead of creating XML file, possibility to define mapping properties via annotation Based on JPA specification (Java Persistence Annotations) The concept of configuration by exception is central to the JPA specification.

19 What is Annotation? Annotation is a specific construction in java 5 for adding additional information to Java source code Annotations are embedded in class files generated by compiler & can be used by other frameworks

20 Annotation Using (element1 = value1, element2 = value2 ( value )

21 Can be used for classes methods variables parameters packages annotations

22 Hibernate Annotations Basic annotations that implement the JPA standard Hibernate extension annotations

23 Annotated Java // Declares this an entity = "people") // Maps the bean to SQL table "people" class Person implements // Map this to the primary key = GenerationType.AUTO) // Database will generate new primary keys private Integer = 32) // Truncate column values to 32 characters. private String name; public Integer getid() { return id; } public void setid(integer id) { this.id = id; } public String getname() { return name; } public void setname(string name) { this.name = name; } }

24 Basic Declares this an Database @OneToMany Relationship mappings & etc.

25 Extension Annotations Contained in org.hibernate.annotations @Check &.etc

26 hibernate.cfg.xml <hibernate-configuration> <session-factory> <property name="hibernate.connection.driver_class">org.hsqldb.jdbcdriver</proper ty> <property name="hibernate.connection.url">jdbc:hsqldb:hsql://localhost/ </property> <property name="hibernate.connection.username">sa</property> <property name="dialect">org.hibernate.dialect.hsqldialect</property> <mapping class="hello.person"/> </session-factory> </hibernate-configuration> --- Annotated Classes

27 Annotations @DiscriminatorValue

28 @Table(name= PROSPECT ) public class Prospect extends Persistent {... public Prospect() {... } } PROSPECT_ID LAST_UPD_BY LAST_UP_TS STUDENT_ID PROSPECT NUMBER(18) NUMBER(18) TIMESTAMP(9) NUMBER(18)

29 @Id Every entity needs a primary key... public abstract class Persistent Long id; }... all Entities require a unique identifier

30 public class Prospect extends public Integer getversion() {... } } The system use the value of Version to detect concurrent modification!

31 @Basic public class Prospect extends = "HS_SELF_REPORTED_CLASS_SIZE") private = "HS_ANTICIPATED_YR_GRAD") private String anticipatedhighschoolgraduationyear; }... PROSPECT PROSPECT_ID NUMBER(18) HS_SELF_REPORTED_CLASS_SIZE NUMBER(5) HS_ANTICIPATED_YR_GRAD CHAR(4)......

32 @Transient Indicates fields that should not be persisted But it could be used for computed/derived data based on the persistent fields of the object it s important to realize is the default So any field that is unannotated in your class will be persisted (or at least attempted) For fields that don t need persistenting they must be marked

33 @Enumerated public enum ProspectStatusEnum { PROSPECT("Prospect"), PROSPECT_INACTIVE( "Prospect Inactive"), PROSPECT_APPLIED( "Prospect Applied"); private String label; ProspectStatusEnum(String label) { } this.label = label; } } public String tostring() { return this.label;

34 @Enumerated... public class Prospect extends = "PRSP_STATUS_EN") ProspectStatusEnum prospectstatusenum;... } EnumType.String will cause the Enum name to be persisted The default is to persist the enum id value (0, 1, 2...) Persisting the name makes the database more readable PROSPECT PRSP_STATUS_EN VARCHAR(25)......

35 @Temporal... public class Prospect extends = "PRSP_STATUS_DT") private Date prospectstatusdate;... } MAUI.PROSPECT PRSP_STATUS_DT DATE......

36 @ManyToOne... public class Prospect extends = "PURGE_SESSION_INFO_ID") private Session purgesession;... } PROSPECT_ID = "SESSION_INFO") public class Session extends Persistent {... } NUMBER(18) PK NUMBER(18) FK SESSION_INFO SESSION_INFO_ID NUMBER(18)......

37 @OneToOne public class Prospect extends = "STUDENT_ID") } private Student student;... PROSPECT PROSPECT_ID NUMBER(18) PK STUDENT_ID NUMBER(18) FK UNIQUE NOT NULL STUDENT_ID NUMBER(18) = "STUDENT") public class Student extends Persistent {... }

38 @OneToMany public class Prospect extends Persistent = "prospect ) private Set<ProspectComment> prospectcomments; } PROSPECT_ID public class ProspectComment extends = "PROSPECT_ID") private Prospect prospect; } NUMBER(18) PK PRSP_COMMENT PRSP_COMMENT_ID NUMBER(18) PK PROSPECT_ID NUMBER(18) FK NOT NULL......

39 public abstract class Persistent private Long = LAST_UPD_TS ) private Date lastupdatedtimestamp;

40 @Inheritance Three strategies Single Table Per Class Hierarchy SINGLE_TABLE Joined Subclass JOINED Table Per Concrete Class TABLE_PER_CLASS

41 Single Table Per (name= insttype, discriminatortype=discriminatortype.string) public abstract class Institution SECONDARY ) public class SecondarySchool extends Institution POST_SECONDARY ) public class PostSecondarySchool extends Institution {}

42 public class Boat implements Serializable {... public class Ferry extends Boat public class AmericaCupClass extends Boat {... }

43 Data Access With Spring

44 Data Access DAO support provides pluggable framework for persistence Currently supports JDBC, Hibernate, JDO, and ibatis Defines consistent exception hierarchy (based on RuntimeException) Provides abstract Support classes for each technology Template methods define specific queries

45 Hibernate Architecture

46 Working with Persistent Objects without Spring Session session = null; Transaction tx = null; try { session = factory.opensession(); tx = session.begintransaction(); session.delete(address); tx.commit(); } finally { } session.close(); Start a Session Transaction is started The object is deleted The transaction is committed The session is closed

47 Spring HibernateTemplate The HibernateTemplate class provides many methods that mirror the methods exposed on the Hibernate Session interface, in addition to a number of convenience methods Typical methods: Delete, find, load, update Execute: you provide a callback and many others

48 Spring HibernateDAOSupport Wraps the HibernateTemplate object public class ReservationDaoImpl extends HibernateDaoSupport implements ReservationDao { public Reservation getreservation (Long orderid) { return (Reservation)getHibernateTemplate().load(Reservation.class, orderid); } public void savereservation (Reservation r) { gethibernatetemplate().saveorupdate(r); } public void remove(reservation Reservation) { gethibernatetemplate().delete(r); }

49 Spring Hibernate Template: execute hibernatetemplate.execute( } }; } new HibernateCallback() { public Object doinhibernate(session session) { Criteria criteria = session.createcriteria(product.class); criteria.add(expression.eq("category", category)); criteria.setmaxresults(6); return criteria.list(); HibernateTemplate is responsible of starting and closing the transaction

50 Spring Hibernate Configuration <bean id="sessionfactory" class="org.springframework.orm.hibernate.localsessionfactorybean"> <property name="datasource"><ref bean="datasource"/></property> <property name="mappingresources"> <list> <value>com/jensenp/reservation/room.hbm.xml</value> <value>com/jensenp/reservation/reservation.hbm.xml</value> <value>com/jensenp/reservation/resource.hbm.xml</value> </list> </property> <property name="hibernateproperties"> <props> <prop key="hibernate.dialect">${hibernate.dialect}</prop> <prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto} </prop> <prop key="hibernate.show_sql">${hibernate.show_sql}</prop> </props> </property> </bean> <bean id= reservationdao" class="com.jensenp.reservation.reservationdaoimpl"> <property name="sessionfactory"><ref bean="sessionfactory"/> </property> </bean>

51 Aspect Oriented Programming

52 Object Oriented Programming In OOP, Applications are reusable Introduced the concept of object initiated a new way to structure applications Developers could visualize systems as groups of entities and the interaction between those entities, which allowed them to tackle larger, more complicated systems and develop them in less time than ever before. 52

53 Looking at Programming Paradigms Where OOP fails us: Technical and functional concerns that are said to be cross-cutting are not easily dealt with using OOP 53

54 Aspect Oriented Programming (AOP) Applications must be concerned with things like: Transaction management Logging Security Do these responsibilities belong to the implementation classes? Should a service class be responsible for transaction management, logging, or security? These concerns are often referred to as crosscutting concerns

55 Looking at Programming Paradigms AOP establishes a certain balance by allowing you to superimpose a new layer onto the datadriven composition of OOP This layer corresponds to the cross-cutting functionalities that are difficult to integrate through OOP paradigm 55

56 Looking at Programming Paradigms What are cross-cutting concerns? Generic functionality that is needed in many places in your application Examples: Logging and Tracing Transaction Management Security Caching Error Handling Performance Monitoring Custom Business Rules 56

57 Looking at Programming Paradigms An Example Requirement: Perform a role-based security check before every application method. 57

58 AOP Paradigm for separating cross-cutting concerns in well-defined software entities called aspects. Does not replace OOP. Complements OOP by modularizing crosscutting concerns. Still a matter of writing classes w/ fields & methods 58

59 Leading AOP Technologies AspectJ Original AOP technology (first version in 1995) Offers a full-blown Aspect Oriented Programming language Uses byte code modification for aspect weaving Spring AOP Java-based AOP framework Uses dynamic proxies for aspect weaving Focuses on using AOP to solve enterprise problems The focus of this session 59

60 AOP Concepts Join Point A point in the execution of a program such as a method call or field assignment Pointcut A collection of joinpoints that you use to define when advice should be executed Advice (the code you want to run) Code to be executed at a Join Point that has been selected by a Pointcut Aspect A module that encapsulates pointcuts and advice Example A typical joinpoint is a method invocation. A typical pointcut is a collection of all method invocations in a particular class 60

61 AOP Concepts: Joinpoint Well-defined point during the execution of your application You can insert additional logic at Joinpoint's Examples of Jointpoint's Method invocation Class initialization Object initialization

62 AOP Concepts: Advice The code that is executed at a particular joinpoint Types of Advice before advice, which executes before joinpoint after advice, which executes after joinpoint around advice, which executes around joinpoint

63 AOP Concepts: Pointcuts A collection of joinpoints that you use to define when advice should be executed By creating pointcuts, you gain fine-grained control over how you apply advice to the components Example A typical joinpoint is a method invocation. A typical pointcut is a collection of all method invocations in a particular class Pointcuts can be composed in complex relationships to further constrain when advice is executed

64 AOP Concepts: Aspects An aspect is the combination of advice and pointcuts

65 AOP Concepts: Weaving Process of actually inserting aspects into the application code at the appropriate point Types of Weaving Compile time weaving Runtime weaving

66 AOP Concepts: Target An object whose execution flow is modified by some AOP process They are sometimes called advised object

67 Types of AOP Static AOP The weaving process forms another step in the build process for an application Example: In Java program, you can achieve the weaving process by modifying the actual bytecode of the application changing and modifying code as necessary Dynamic AOP The weaving process is performed dynamically at runtime Easy to change the weaving process without recompilation

68 Spring Architecture The seven modules of the Spring framework 68

69 Intro to Spring AOP In Spring, aspects are woven into Spring-managed beans at runtime by wrapping them with a proxy class. Spring aspects are implemented as proxies that wrap the target object. The proxy handles method calls, performs additional aspect logic, and then invokes the target method. Spring does not create a proxied object until that proxied bean is needed by the application. 69

70