Hibernate Tutorial

HIBERNATE TUTORIAL HIBERNATE - Introduction to Hibernate Hibernate is an open source object/relational mapping tool for Java. Hibernate lets you develop persistent classes following common Java idiom - including association, inheritance, polymorphism, composition and the Java collections framework. Hibernate not only takes care of the mapping from Java classes to database tables (and from Java data types to SQL data types), but also provides data query and retrieval facilities and can significantly reduce development time otherwise spent with manual data handling in SQL and JDBC. Hibernates goal is to relieve the developer from 95 percent of common data persistence related programming tasks. Hibernate is Free Software. The LGPL license is sufficiently flexible to allow the use of Hibernate in both open source and commercial projects (see the LicenseFAQ for details). Hibernate is available for download at http://www.hibernate.org/. This tutorial aims to provide insight into Hibernate version 3.0RC and its usage Some of the main features of hibernate are listed below and we have tried to explain some of them in detail later in this tutorial.

Transparent persistence without byte code processing Transparent persistence JavaBeans style properties are persisted No build-time source or byte code generation / processing Support for extensive subset of Java collections API Collection instance management Extensible type system Constraint transparency Automatic Dirty Checking Detached object support Object-oriented query language Powerful object-oriented query language Full support for polymorphic queries New Criteria queries Native SQL queries Object / Relational mappings Three different O/R mapping strategies Multiple-objects to single-row mapping Polymorphic associations Bidirectional associations Association filtering Collections of basic types Indexed collections Composite Collection Elements Lifecycle objects Automatic primary key generation Multiple synthetic key generation strategies Support for application assigned identifiers Support for composite keys Object/Relational mapping definition XML mapping documents Human-readable format XDoclet support HDLCA (Hibernate Dual-Layer Cache Architecture) Thread safeness Non-blocking data access Session level cache Optional second-level cache Optional query cache Works well with others High performance Lazy initialization Outer join fetching

Hibernate High level architecture of Hibernate can be described as shown in following illustration.

Hibernate makes use of persistent objects commonly called as POJO (POJO = "Plain Old Java Object".) along with XML mapping documents for persisting objects to the database layer. The term POJO refers to a normal Java objects that does not serve any other special role or implement any special interfaces of any of the Java frameworks (EJB, JDBC, DAO, JDO, etc...). Rather than utilize byte code processing or code generation, Hibernate uses runtime reflection to determine the persistent properties of a class. The objects to be persisted are defined in a mapping document, which serves to describe the persistent

fields and associations, as well as any subclasses or proxies of the persistent object. The mapping documents are compiled at application startup time and provide the framework with necessary information for a class. Additionally, they are used in support operations, such as generating the database schema or creating stub Java source files. Typical Hibernate code sessionFactory = new Configuration().configure().buildSessionFactory(); Session session = sessionFactory.openSession(); Transaction tx = session.beginTransaction(); Customer newCustomer = new Customer(); newCustomer.setName("New Customer"); newCustomer.setAddress("Address of New Customer"); newCustomer.setEmailId("[email protected]"); session.save(newCustomer); tx.commit(); session.close(); First step is hibernate application is to retrieve Hibernate Session; Hibernate Session is the main runtime interface between a Java application and Hibernate. SessionFactory allows applications to create hibernate session by reading hibernate configurations file hibernate.cfg.xml. After specifying transaction boundaries, application can make use of persistent java objects and use session for persisting to the databases.

HIBERNATE TUTORIAL HIBERNATE - Features of Hibernate

Transparent persistence without byte code processing Transparent persistence JavaBeans style properties are persisted No build-time source or byte code generation / processing Support for extensive subset of Java collections API Collection instance management Extensible type system Constraint transparency Automatic Dirty Checking Detached object support Object-oriented query language Powerful object-oriented query language Full support for polymorphic queries New Criteria queries Native SQL queries Object / Relational mappings Three different O/R mapping strategies Multiple-objects to single-row mapping Polymorphic associations Bidirectional associations Association filtering Collections of basic types Indexed collections Composite Collection Elements Lifecycle objects Automatic primary key generation Multiple synthetic key generation strategies Support for application assigned identifiers Support for composite keys Object/Relational mapping definition XML mapping documents Human-readable format XDoclet support HDLCA (Hibernate Dual-Layer Cache Architecture) Thread safeness Non-blocking data access Session level cache Optional second-level cache Optional query cache Works well with others High performance Lazy initialization Outer join fetching

HIBERNATE TUTORIAL HIBERNATE - Getting Started With Hibernate Hibernate is Free Software. The LGPL license is sufficiently flexible to allow the use of Hibernate in both open source and commercial projects (see the LicenseFAQ for details). Hibernate is available for download at http://www.hibernate.org/ We wll take up an simple java example that authenticates users based on the credentials to get started with hibernate.

HIBERNATE TUTORIAL HIBERNATE - Getting Started With Hibernate Preparing Database Let’s consider a simple database schema with a singe table as APPLABSUSER.

CREATE TABLE `applabsuser` ( `USER_ID` int(11) NOT NULL default '0', `USER_NAME` varchar(255) NOT NULL default '', `USER_PASSWORD` varchar(255) NOT NULL default '', `USER_FIRST_NAME` varchar(255) default NULL, `USER_LAST_NAME` varchar(255) default NULL, `USER_EMAIL` varchar(255) default NULL, `USER_CREATION_DATE` date default NULL, `USER_MODIFICATION_DATE` date default NULL, PRIMARY KEY (`USER_ID`), UNIQUE KEY `USER_NAME` (`USER_NAME`) );

HIBERNATE TUTORIAL HIBERNATE - Getting Started With Hibernate Creating persistent java objects Hibernate works best with the Plain Old Java Objects programming model for persistent classes. Hibernate is not restricted in its usage of property types, all Java JDK types and primitives (like String, char and Date) can be mapped, including classes from the Java collections framework. You can map them as values, collections of values, or associations to other entities. The id is a special property that represents the database identifer (primary key) of that class, Hibernate can use identifiers only internally, but we would lose some of the flexibility in our application architecture. No special interface has to be implemented for persistent classes nor do you have to subclass from a special root persistent class. Hibernate also doesn't require any build time processing, such as byte-code manipulation, it relies solely on Java reflection and runtime class enhancement (through CGLIB). So, without any dependency of the POJO class on Hibernate, we can map it to a database table. Following code sample represents a java object structure which represents the AppLabsUser table. Generally these domain objects contain only getters and setters methods. One can use Hibernate extension toolset to create such domain objects. AppLabsUser.java

package org.applabs.quickstart; import java.io.Serializable; import java.util.Date; import org.apache.commons.lang.builder.ToStringBuilder; public class AppLabsUser implements Serializable {

public void setName(String name) { /** identifier field */ private Long id; /** persistent field */ private String userName; /** persistent field */ private String userPassword; /** persistent field */ private String userFirstName; /** persistent field */ private String userLastName; /** persistent field */ private String userEmail; /** persistent field */ private Date userCreationDate; /** persistent field */ private Date userModificationDate; /** full constructor */ public Applabsuser(String userName, String userPassword, String userFirstName, String userLastName, String userEmail, Date userCreationDate, Date userModificationDate) { this.userName = userName; this.userPassword = userPassword; this.userFirstName = userFirstName; this.userLastName = userLastName; this.userEmail = userEmail; this.userCreationDate = userCreationDate; this.userModificationDate = userModificationDate; } /** default constructor */ public Applabsuser() {

HIBERNATE TUTORIAL HIBERNATE - Getting Started With Hibernate Mapping POJO with persistence layer using hibernate mapping document Each persistent class needs to be mapped with its configuration file. Following code represents Hibernate mapping file for AppLabsUser class. <property column="USER_NAME" length="255" name="userName" not-null="true" type="java.lang.String"/> <property column="USER_PASSWORD" length="255" name="userPassword" not-null="true" type="java.lang.String"/> <property column="USER_FIRST_NAME" length="255" name="userFirstName" type="java.lang.String"/> <property column="USER_LAST_NAME" length="255" name="userLastName" type="java.lang.String"/> <property column="USER_EMAIL" length="255" name="userEmail" type="java.lang.String"/> <property column="USER_CREATION_DATE" length="10" name="userCreationDate" type="java.util.Date"/> <property column="USER_MODIFICATION_DATE" length="10" name="userModificationDate" type="java.util.Date"/> One can also generate Hibernate mapping documents using Hibernate extension toolset. Hibernate mapping documents are straight forward. The element maps a table with corresponding class. The element represents the primary key column, and its associated attribute in the domain object. The <property> elements represent all other attributes available in the domain object.

HIBERNATE TUTORIAL HIBERNATE - Getting Started With Hibernate Hibernate Configuration File Hibernate configuration file information needed to connect to persistent layer and the linked mapping documents. You can either specify the data source name or JDBC details that are required for hibernate to make JDBC connection to the database. The element <mapping-resource> refers to the mapping document that contains mapping for domain object and hibernate mapping

document. <session-factory> <property name="show_sql">true <property name="hibernate.dialect">org.hibernate.dialect.MySQLMyISAMDialect <property name="hibernate.connection.driver_class">org.gjt.mm.mysql.Driver <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/applabs <property name="hibernate.connection.username">root <property name="hibernate.connection.password">r00Tp@$wd <mapping resource="org/applabs/hibernate/quickstart/Applabsuser.hbm.xml"/>

HIBERNATE TUTORIAL HIBERNATE - Getting Started With Hibernate Hibernate Configuration File Hibernate configuration file information needed to connect to persistent layer and the linked mapping documents. You can either specify the data source name or JDBC details that are required for hibernate to make JDBC connection to the database. The element <mapping-resource> refers to the mapping document that contains mapping for domain object and hibernate mapping document.

<session-factory> <property name="show_sql">true <property name="hibernate.dialect">org.hibernate.dialect.MySQLMyISAMDialect <property name="hibernate.connection.driver_class">org.gjt.mm.mysql.Driver <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/applabs <property name="hibernate.connection.username">root <property name="hibernate.connection.password">r00Tp@$wd <mapping resource="org/applabs/hibernate/quickstart/Applabsuser.hbm.xml"/>

HIBERNATE TUTORIAL HIBERNATE - Getting Started With Hibernate Hibernate Sample Code (Inserting new record) Here is how you can use Hibernate in your programs. Typical Hibernate programs begin with configuration that is required for Hibernate. Hibernate can be configured in two ways. Programmatically and Configuration file based. In Configuration file based mode, hibernate looks for configuration file “hibernate.cfg.xml” in the claspath. Based on the resource mapping provided hibernate creates mapping of tables and domain objects. In the programmatic configuration method, the details such as JDBC connection details and resource mapping details etc are supplied in the program using Configuration API. Following example shows programmatic configuration of hibernate.

Configuration config = new Configuration() .addResource("org/applabs/hibernate/quickstart/Applabsuser.hbm.xml") Configuration config = new Configuration() .addClass(org.hibernate.quickstart.Applabsuser.class) .setProperty("hibernate.dialect", "org.hibernate.dialect. MySQLMyISAMDialect") .setProperty("hibernate.connection.driver_class", " org.gjt.mm.mysql.Driver") . . . SessionFactory sessions = config.buildSessionFactory(); In configuration file based approach, “hibernate.cfg.xml” is placed in the classpath, Following Hibernate code can be used in this method.

SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); Session session = sessionFactory.openSession(); AppLabsUser user = new AppLabsUser(); Transaction tx = session.beginTransaction(); user.setUserCreationDate(new Date()); user.setUserEmail("[email protected]"); user.setUserFirstName("userFirstName"); user.setUserLastName("userLastName"); user.setUserName("userName-1"); user.setUserPassword("userPassword"); session.saveOrUpdate(user); tx.commit(); session.close();

HIBERNATE - Getting Started With Hibernate Hibernate Sample Code (Quering the database) SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); Session session = sessionFactory.openSession(); ArrayList arrayList = null; String SQL_STRING = "FROM AppLabsUser as users"; Query query = session.createQuery(SQL_STRING); ArrayList list = (ArrayList)query.list(); for(int i=0; i<list.size();i++){ System.out.println(list.get(i)); } session.close();

HIBERNATE - Hibernate O/R Mapping This section will explain how to write the mapping documents manually. Although there are tools available to create these mapping documents, learning how to create these documents manually helps in fine tuning and setting up advance table mapping.

Mapping Declaration Object/relational mappings are usually defined in XML document. The mapping language is Java-centric, meaning that mappings are constructed around persistent class declarations, not table declarations. Mapping Document The above example shows a typical mapping document that contains class mapping with table. All mapping XML document should refer to hibernate-mapping-3.0.dtd via doctype.

HIBERNATE TUTORIAL HIBERNATE - Hibernate O/R Mapping element

The element maps the domain object with corresponding entity in the database. hibernate-mapping element allows you to nest several persistent mappings, as shown above. It is however good practice to map only a single persistent class in one mapping file and name it after the persistent superclass, e.g. User.hbm.xml, Group.hbm.xml.
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name (optional): The fully qualified Java class name of the persistent class (or interface). If this attribute is missing, it is assumed that the mapping is for a non-POJO entity. table (optional - defaults to the unqualified class name): The name of its database table. discriminator-value (optional - defaults to the class name): A value that distiguishes individual subclasses, used for polymorphic behaviour. Acceptable values include null and not null. mutable (optional, defaults to true): Specifies that instances of the class are (not) mutable. schema (optional): Override the schema name specified by the root element. catalog (optional): Override the catalog name specified by the root element. proxy (optional): Specifies an interface to use for lazy initializing proxies. You may specify the name of the class itself.

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dynamic-update (optional, defaults to false): Specifies that UPDATE SQL should be generated at runtime and contain only those columns whose values have changed.

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dynamic-insert (optional, defaults to false): Specifies that INSERT SQL should be generated at runtime and contain only the columns whose values are not null.

HIBERNATE TUTORIAL HIBERNATE - Hibernate O/R Mapping element The element defines the mapping from that property to the primary key column. Mapped classes must declare the primary key column of the database table. Most classes will also have a JavaBeans-style property holding the unique identifier of an instance.

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name (optional): The name of the identifier property. type (optional): A name that indicates the Hibernate type. column (optional - defaults to the property name): The name of the primary key column. unsaved-value (optional - defaults to a "sensible" value): An identifier property value that indicates that an instance is newly instantiated (unsaved), distinguishing it from detached instances that were saved or loaded in a previous session. access (optional - defaults to property): The strategy Hibernate should use for accessing the property value.

HIBERNATE - Hibernate O/R Mapping element The optional child element names a Java class used to generate unique identifiers for instances of the persistent class. If any parameters are required to configure or initialize the generator instance, they are passed using the <param> element. <param name="table">uid_table <param name="column">next_hi_value_column All generators implement the interface org.hibernate.id.IdentifierGenerator. This is a very simple interface; some applications may choose to provide their own specialized implementations. However, Hibernate provides a range of built-in implementations.

There are shortcut names for the built-in generators: increment identity sequence hilo

seqhilo uuid guid native assigned select foreign

generates identifiers of type long, short or int that are unique only when no other process is inserting data into the same table. Do not use in a cluster. . supports identity columns in DB2, MySQL, MS SQL Server, Sybase and HypersonicSQL. The returned identifier is of type long, short or int. uses a sequence in DB2, PostgreSQL, Oracle, SAP DB, McKoi or a generator in Interbase. The returned identifier is of type long, short or int uses a hi/lo algorithm to efficiently generate identifiers of type long, short or int, given a table and column (by default hibernate_unique_key and next_hi respectively) as a source of hi values. The hi/lo algorithm generates identifiers that are unique only for a particular database. uses a hi/lo algorithm to efficiently generate identifiers of type long, short or int, given a named database sequence. uses a 128-bit UUID algorithm to generate identifiers of type string, unique within a network (the IP address is used). The UUID is encoded as a string of hexadecimal digits of length 32. uses a database-generated GUID string on MS SQL Server and MySQL. picks identity, sequence or hilo depending upon the capabilities of the underlying database. lets the application to assign an identifier to the object before save() is called. This is the default strategy if no element is specified. retrieves a primary key assigned by a database trigger by selecting the row by some unique key and retrieving the primary key value uses the identifier of another associated object. Usually used in conjunction with a primary key association.

HIBERNATE - Hibernate O/R Mapping <property> element The <property> element declares a persistent, JavaBean style property of the class. <property name="propertyName" (1) column="column_name" (2) type="typename" (3) update="true|false" (4) insert="true|false" (4) formula="arbitrary SQL expression" (5) access="field|property|ClassName" (6) lazy="true|false" (7) unique="true|false" (8) not-null="true|false" (9) optimistic-lock="true|false" (10) /> All generators implement the interface org.hibernate.id.IdentifierGenerator. This is a very simple interface; some applications may choose to provide their own specialized implementations. However, Hibernate provides a range of built-in implementations.

There are shortcut names for the built-in generators: (1) (2)

name: the name of the property, with an initial lowercase letter. column (optional - defaults to the property name): the name of the mapped database table column. This may also be specified by nested element(s). type (optional): a name that indicates the Hibernate type. update, insert (optional - defaults to true) : specifies that the mapped columns should be included in SQL UPDATE and/or INSERT statements. Setting both to false allows a pure "derived" property whose value is initialized from some other property that maps to the same colum(s) or by a trigger or other application. formula (optional): an SQL expression that defines the value for a computed property. Computed properties do not have a column mapping of their own. access (optional - defaults to property): The strategy Hibernate should use for accessing the property value. lazy (optional - defaults to false): Specifies that this property should be fetched lazily when the instance variable is first accessed (requires build-time bytecode instrumentation).

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unique (optional): Enable the DDL generation of a unique constraint for the columns. Also, allow this to be the target of a property-ref.

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not-null (optional): Enable the DDL generation of a nullability constraint for the columns.

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optimistic-lock (optional - defaults to true): Specifies that updates to this property do or do not require acquisition of the optimistic lock. In other words, determines if a version increment should occur when this property is dirty. typename could be: • • •

The name of a Hibernate basic type (eg. integer, string, character, date, timestamp, float, binary, serializable, object, blob). The name of a Java class with a default basic type (eg. int, float, char, java.lang.String, java.util.Date, java.lang.Integer, java.sql.Clob). The name of a serializable Java class.

• The class name of a custom type (eg. com.illflow.type.MyCustomType). An especially powerful feature are derived properties. These properties are by definition read-only, the property value is computed at load time. You declare the computation as a SQL expression, this translates to a SELECT clause subquery in the SQL query that loads an instance: <property name="totalPrice" formula="( SELECT SUM (li.quantity*p.price) FROM LineItem li, Product p WHERE li.productId = p.productId AND li.customerId = customerId AND li.orderNumber = orderNumber )"/>

HIBERNATE TUTORIAL HIBERNATE - Hibernate O/R Mapping

<many-to-one> element

An ordinary association to another persistent class is declared using a many-to-one element. The relational model is a many-to-one association: a foreign key in one table is referencing the primary key column(s) of the target table. <many-to-one name="propertyName" column="column_name" class="ClassName" cascade="cascade_style" fetch="join|select" update="true|false" insert="true|false" property-ref="propertyNameFromAssociatedClass" access="field|property|ClassName" unique="true|false" not-null="true|false" optimistic-lock="true|false" lazy="true|false" entity-name="EntityName"

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name: The name of the property. column (optional): The name of the foreign key column. This may also be specified by nested element(s). class (optional - defaults to the property type determined by reflection): The name of the associated class. cascade (optional): Specifies which operations should be cascaded from the parent object to the associated object. join (optional - defaults to select): Chooses between outer-join fetching or sequential select fetching. update, insert (optional - defaults to true) specifies that the mapped columns should be included in SQL UPDATE and/or INSERT statements. Setting both to false allows a pure "derived" association whose value is initialized from some other property that maps to the same colum(s) or by a trigger or other application. property-ref: (optional) The name of a property of the associated class that is joined to this foreign key. If not specified, the primary key of the associated class is used. access (optional - defaults to property): The strategy Hibernate should use for accessing the property value. unique (optional): Enable the DDL generation of a unique constraint for the foreign-key column. Also, allow this to be the target of a property-ref. This makes the association multiplicity effectively one to one. not-null (optional): Enable the DDL generation of a nullability constraint for the foreign key columns.

optimistic-lock (optional - defaults to true): Specifies that updates to this property do or do not require acquisition of the optimistic lock. In other words, dertermines if a version increment should occur when this property is dirty. (12) lazy (optional - defaults to false): Specifies that this property should be fetched lazily when the instance variable is first accessed (requires build-time bytecode instrumentation). A typical many-to-one declaration looks as simple as this:

HIBERNATE - Hibernate O/R Mapping element A one-to-one association to another persistent class is declared using a one-to-one element. . (1) (2) (3) (4)

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name: The name of the property. class (optional - defaults to the property type determined by reflection): The name of the associated class. cascade (optional) specifies which operations should be cascaded from the parent object to the associated object. constrained (optional) specifies that a foreign key constraint on the primary key of the mapped table references the table of the associated class. This option affects the order in which save() and delete() are cascaded, and determines whether the association may be proxied (it is also used by the schema export tool). fetch (optional - defaults to select): Chooses between outer-join fetching or sequential select fetching. property-ref: (optional) The name of a property of the associated class that is joined to the primary key of this class. If not specified, the primary key of the associated class is used. access (optional - defaults to property): The strategy Hibernate should use for accessing the property value.

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formula (optional): Almost all one to one associations map to the primary key of the owning entity. In the rare case that this is not the case, you may specify a some other column, columns or expression to join on using an SQL formula. (See org.hibernate.test.onetooneformula for an example.) A typical many-to-one declaration looks as simple as this: <many-to-one name="product" class="Product" column="PRODUCT_ID"/>

HIBERNATE - Hibernate Mapping In Depth Hibernate allows the mapping of Mapped tables with the domain objects using the persistent collection-valued fields. These fields needs be declared as an interface type. The actual interface can be java.util.Set, java.util.Collection, java.util.List, java.util.Map, java.util.SortedSet, java.util.SortedMap or custom implementations of org.hibernate.usertype.UserCollectionType Collections instances have the usual behavior of value types. They are automatically persisted when referenced by a persistent object and automatically deleted when unreferenced. If a collection is passed from one persistent object to another, its elements might be moved from one table to another. Two entities may not share a reference to the same collection instance. Due to the

underlying relational model, collection-valued properties do not support null value semantics; public class Product { private String serialNumber; private Set parts = new HashSet(); public Set getParts() { return parts; } void setParts(Set parts) { this.parts = parts; } public String getSerialNumber() { return serialNumber; } void setSerialNumber(String sn) { serialNumber = sn; } } Collection Mapping <map name="propertyName" table="table_name" schema="schema_name" lazy="true|false" inverse="true|false" cascade="all|none|save-update|delete|all-delete-orphan" sort="unsorted|natural|comparatorClass" order-by="column_name asc|desc" where="arbitrary sql where condition" fetch="join|select" batch-size="N" access="field|property|ClassName" optimistic-lock="true|false" > <map-key .... /> <element .... />



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name the collection property name table (optional - defaults to property name) the name of the collection table (not used for one-to-many associations) schema (optional) the name of a table schema to override the schema declared on the root element lazy (optional - defaults to true) enable lazy initialization (not available for arrays) inverse (optional - defaults to false) mark this collection as the "inverse" end of a bidirectional association cascade (optional - defaults to none) enable operations to cascade to child entities

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sort (optional) specify a sorted collection with natural sort order, or a given comparator class

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order-by (optional, JDK1.4 only) specify a table column (or columns) that define the iteration order of the Map, Set or bag, together with an optional asc or desc

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where (optional) specify an arbitrary SQL WHERE condition to be used when retrieving or removing the collection (useful if the collection should contain only a subset of the available data)

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fetch (optional, defaults to select) Choose between outer-join fetching and fetching by sequential select. Only one collection may be fetched by outer join per SQL SELECT.

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batch-size (optional, defaults to 1) specify a "batch size" for lazily fetching instances of this collection.

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access (optional - defaults to property): The strategy Hibernate should use for accessing the property value.

optimistic-lock (optional - defaults to true): Species that changes to the state of the collection results in increment of the owning entity's version. (For one to many associations, it is often reasonable to disable this setting.) These are some more mapings which we will discuss later (13)

Association Mapping Component Mapping

HIBERNATE TUTORIAL HIBERNATE - Hibernate Query Language

Hibernate is equipped with an extremely powerful query language that looks very much like SQL. Queries are caseinsensitive, except for names of Java classes and properties.

Clause The from clause The simplest possible Hibernate query is of the form: From org.applabs.base.User From User which simply returns all instances of the class org.applabs.base.User. Most of the time, you will need to assign an alias, since you will want to refer to the User in other parts of the query. from User as user This query assigns the alias user to User instances, so we could use that alias later in the query. The as keyword is optional; we could also write: from User user Multiple classes may appear, resulting in a cartesian product or "cross" join. from User, Group from User as user, Group as group

The select clause The select clause picks which objects and properties to return in the query result set. Queries may return properties of any value type including properties of component type: select user.name from User user where user.name like 'mary%' select customer.contact.firstName from Customer as cust

The where clause The where clause allows you to narrow the list of instances returned. from User as user where user.name='mary'

HIBERNATE - Hibernate Complete Example In this section we will extend our quick start sample into to a web based application that comprises of struts and Hibernate support. Introduction In this example we will build a simple web based document repository application using hibernate. The document repository under consideration will have categorization of the documents based on the topics (Folder based like structure), Keywords for each document (this will simplify searches), versioning for each document, Document modification history, permissions based access for each entity based on users and groups. Database scheme. The concept of properties tables: Here we have extended the concept of Hash tables to the database, Instead of adding more and more columns as per growing needs A properties table is created per Entity, Each property (Prop) table contains name and value pair that stores additional information for particular entity, thus you can store as many properties as you want for a given entity. Getter and setter methods need to be provided from the domain object so that we can represent these properties inside domain objects. Basic entities. Basic entities such as User, Group, and Permissions along with Prop tables for each are provided to persistent data for corresponding entities, Now as a business rule a group contains multiple Users and One User can be a part of multiple Groups. Each entity, User, Group, and Permission have UserProp, GroupProp and PremissionProp respectively. The relation between Entity and Prop is one to many. E.g. User can have multiple Properties. (For simplicity, Permission tables are not shown in the model) Categories and Documents Category refers to a Folder/Directory like structure on the file system. Each category may or may not have its Parent Category. Category contains information like name, description, creation details, modification deleted and deletion details. Each category can have multiple entries. (Each Folder can contain one or more Documents (Entries) in it. Each Document can have one or more versions in it.(Document corresponds to version). Document contains information such as Title, Body, Summary, life cycle details, version number, keywords, workflow status, Entry details and Attachment details; Document also contains properties associated with it. Attachment is a file associated with each Document, Database stores the name of file stored on the file system and the size of Attachment.

HIBERNATE TUTORIAL HIBERNATE - Hibernate Complete Example Database Scripts

--Drop Tables DROP TABLE "APP"."ATTACHMENT"; DROP TABLE "APP"."CATEGORY"; DROP TABLE "APP"."CATEGORY_PROP"; DROP TABLE "APP"."DOCUMENT"; DROP TABLE "APP"."DOCUMENT_ATTACHMENT"; DROP TABLE "APP"."DOCUMENT_KEYWORDS"; DROP TABLE "APP"."DOCUMENT_PROP"; DROP TABLE "APP"."ENTRY"; DROP TABLE "APP"."GROUP"; DROP TABLE "APP"."GROUP_PROP"; DROP TABLE "APP"."IDGENERATOR"; DROP TABLE "APP"."KEYWORD"; DROP TABLE "APP"."USER"; DROP TABLE "APP"."USER_GROUP"; DROP TABLE "APP"."USER_PROP"; -- Table: "APP"."ATTACHMENT" CREATE TABLE "APP"."ATTACHMENT" ( "ATTACHMENT_ID" numeric NOT NULL, "DOCUMENT_ID" numeric, "ATTACHMEMT_PATH" varchar, "ATTACHMENT_SIZE" numeric, CONSTRAINT "ATTACHMENT_pkey" PRIMARY KEY ("ATTACHMENT_ID") ); -- Table: "APP"."CATEGORY" CREATE TABLE "APP"."CATEGORY" ( "CATAGORY_ID" numeric NOT NULL, "CATEGORY_NAME" varchar, "CATEGORY_DESCRIPTION" varchar, "CREATED_BY" numeric, "CREATION_DATE" date, "MODIFIED_BY" numeric, "MODIFICATION_DATE" date, "DELETED_BY" numeric, "DELETE_DATE" date, "PARENT_CATAGORY" numeric, CONSTRAINT "CATEGORY_pkey" PRIMARY KEY ("CATAGORY_ID"), CONSTRAINT "CATEGORY_PARENT_CATAGORY_fkey" FOREIGN KEY ("PARENT_CATAGORY") REFERENCES "APP"."CATEGORY" ("CATAGORY_ID") ON UPDATE NO ACTION ON DELETE NO ACTION, CONSTRAINT authorfk FOREIGN KEY ("CREATED_BY") REFERENCES "APP"."USER" ("USER_ID") ON UPDATE NO ACTION ON DELETE NO ACTION, CONSTRAINT deletorfk FOREIGN KEY ("DELETED_BY") REFERENCES "APP"."USER" ("USER_ID") ON UPDATE NO ACTION ON DELETE NO ACTION,

HIBERNATE - Hibernate Complete Example Database Tables Overview

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HIBERNATE - Hibernate Complete Example hbm files User.hbm.xml <param name="table">idgen <param name="column">NEXT <property column="USER_NAME" name="userName" type="java.lang.String"/> <property column="USER_PASSWORD" name="userPassword" type="java.lang.String"/> <property column="USER_FIRST_NAME" name="userFirstName" type="java.lang.String"/> <property column="USER_EMAIL" name="userEmail" type="java.lang.String"/> <property column="USER_LAST_NAME" name="userLastName" type="java.lang.String"/> <property column="CREATION_DATE" length="4" name="creationDate" type="java.util.Date"/> <property column="CREATED_BY" name="createdBy" type="java.lang.Double"/> <property column="MODIFICATION_DATE" length="4" name="modificationDate" type="java.util.Date"/> <property column="MODIFIED_BY" name="modifiedBy" type="java.lang.Double"/> <property column="DELETE_DATE" length="4" name="deleteDate" type="java.util.Date"/> <property column="DELETED_BY" name="deletedBy" type="java.lang.Double"/> <set name="properties" lazy="true" inverse="true" cascade="all-delete-orphan"> UserProp.hbm.xml

<param name="table">idgen <param name="column">NEXT <property column="CATEGORY_NAME" name="categoryName" type="java.lang.String"/> <property column="CATEGORY_DESCRIPTION" name="categoryDescription" type="java.lang.String"/> <property column="CREATED_BY" name="createdBy" type="java.lang.Double"/> <property column="CREATION_DATE" length="4" name="creationDate" type="java.util.Date"/> <property column="MODIFIED_BY" name="modifiedBy" type="java.lang.Double"/> <property column="MODIFICATION_DATE" length="4" name="modificationDate" type="java.util.Date"/> <property column="DELETED_BY" name="deletedBy" type="java.lang.Double"/> <property column="DELETE_DATE" length="4" name="deleteDate" type="java.util.Date"/> <set name="childCatagories"> <set name="properties" lazy="true" inverse="true" cascade="all-delete-orphan"> Category.hbm.xml

<param name="table">idgen <param name="column">NEXT <property column="CATEGORY_NAME" name="categoryName" type="java.lang.String"/> <property column="CATEGORY_DESCRIPTION" name="categoryDescription" type="java.lang.String"/> <property column="CREATED_BY" name="createdBy" type="java.lang.Double"/> <property column="CREATION_DATE" length="4" name="creationDate" type="java.util.Date"/> <property column="MODIFIED_BY" name="modifiedBy" type="java.lang.Double"/> <property column="MODIFICATION_DATE" length="4" name="modificationDate" type="java.util.Date"/> <property column="DELETED_BY" name="deletedBy" type="java.lang.Double"/> <property column="DELETE_DATE" length="4" name="deleteDate" type="java.util.Date"/> <set name="childCatagories"> <set name="properties" lazy="true" inverse="true" cascade="all-delete-orphan"> CategoryProp.hbm.xml

<param name="table">idgen <param name="column">NEXT <property column="CATEGORY_ID" name="categoryId" type="java.lang.Long"/> <property column="PROP_NAME" name="propName" type="java.lang.String"/> <property column="PROP_VALUE" name="propValue" type="java.lang.String"/> Document.hbm.xml <property column="DOCUMENT_TITLE" name="documentTitle" type="java.lang.String"/> <property column="DOCUMENT_BODY" name="documentBody" type="java.lang.String"/> <property column="DOCUMENT_SUMMARY" name="documentSummary" type="java.lang.String"/> <property column="CREATED_BY" length="65535" name="createdBy" type="java.lang.Double"/> <property column="CREATION_DATE" length="4" name="creationDate" type="java.util.Date"/> <property column="MODIFIED_BY" length="65535" name="modifiedBy" type="java.lang.Double"/> <property column="MODIFICATION_DATE" length="4" name="modificationDate" type="java.util.Date"/> <property column="DELETED_BY" length="65535" name="deletedBy" type="java.lang.Double"/> <property column="DELETED_DATE" length="4" name="deletedDate" type="java.util.Date"/> <property column="DOCUMENT_VERSION" length="65535" name="documentVersion" type="java.lang.Double"/> <property column="DOCUMENT_STATUS" length="65535" name="documentStatus" type="java.lang.Double"/> <property column="ENTRY_ID" length="65535" name="entryId" type="java.lang.Double"/> DocumentProp.hbm.xml

<property column="document_id" length="65535" name="documentId" not-null="true" type="java.lang.Double"/> <property column="prop_name" name="propName" not-null="true" type="java.lang.String"/> <property column="prop_value" name="propValue" type="java.lang.String"/> <property column="prop_value_details" name="propValueDetails" type="java.lang.String"/>