JAVA PERSISTENCE API PDF
One of the problems of Object Orientation is how to map the objects as the database requires. It is possible to have a class with the name Car but its data is . JAVA PERSISTENCE API (JPA). 3. About the Tutorial. This tutorial provides a basic understanding of how to store a copy of database objects into temporary. Linda DeMichiel, Oracle. Lukas Jungmann, Oracle. JSR Java. TM. Persistence API, Version July 17, Version , Maintenance.
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The Java Persistence API. – Java Persistence Query Language (JPQL). – The Java Persistence Criteria API. – O/R mapping metadata (Persistence Annotations ). Pro JPA 2. Mastering the Java™ Persistence API. □ □ □. Mike Keith and. Merrick Schnicariol .. Java Support for Persistence. The Java Persistence API Storing and loading objects □. Working with detached entity instances Using Java Persistence in EJB.
Features that may not be able to be addressed in Java Persistence 2. The goal of the proposed specification is to address the needs of the Java community by adding functionality to the Java Persistence API to address requests received from the members of the community.
See 2. The Java Persistence 2. The API Specification will continue to use the javax.
The primary means of communication will be email and conference calls. Face-to-face meetings will be scheduled if needed. This information will be available in all spec drafts and on the Update page of the JSR.
We intend this to be the case.
One of the most important characteristics nowadays is cache. Concluding, annotations reduce the work of heavy coding and ensure a consistent mapping between entities data base and classes application as shown in figure 4. The need to implement the code by hand should be discarded with the 6 purpose of keeping consistency between the dbschema A stored procedure is a subroutine stored in the and the classes generated POJOs.
Above and beyond, there are many annotations like table, Transient, EmbeddedID, etc. SQL sentence  example in Hibernate see figure 10 , where a stored procedure figure 9 is trying to be called, but it is not There are two ways to mapping relational data to objects successfully running, returning an exception related to the in a proper manner and automatically by using IDE tools return type and generates an exception figure 11 , some like Netbeans for example: One of them is developing the programmers still need to use some stored procedures to entities classes with the use of annotations and then support legacy systems or simply some SP with logic building the dbschema db script ; the other approach is inside; for this reason stored procedures is still supported building the database first, and then by using reverse by JPA implementations.
TopLink implements SP calls engineering, the entities can be generated and mapped by means of annotations like through annotations; any way, consistence between Entity NamedStoredProcedureQuery .
Concluding, the — Relational E-R and Object Oriented OO models is developer must manage all mapping result issues when carried out in JPA because annotations track all kind of using stored procedures, and they depend on the JPA characteristics of a relational database to a class diagram implementation provider.
According to Enterprise Figure9: On the other hand, The use of the Java Exception message from SP call using cache. In addition, and in order to facilitate the coding of createNativeQuery  business rules that depend on SQL statements execution with an object oriented approach inside the application 4.
JPA relieves the do with the database that is used, which in this example is programmer from manual handling of persistent data in MySQL see figure 6 ; whereas, in JDBC it is necessary CRUD operations, hence reducing the development time to change queries format depending on the database that and maintenance cost, it is enough to provide the data is being used and it is dependent on the schema; in spite base schema to generate automatically the most of the of the fact that in JDBC 4.
Ease of data persistence: The developer characteristics.
The JPA implementations e. Additionally, annotations configuration files and Java annotations provide the can help JDBC applications to improve data persistence. In JPA, the access the developer has to implement hand coding to manage information like database name, server, user and cache or to optimize SQL sentences. Stored procedures do JDBC, the programmer has to write a bulk of code nothing to really help the application developer in relation to establish and close the connection with database, and to cache; they are procedure - based and cannot be cached for every operation, the developer needs to call methods except for what the database server may provide in e.
Although, in the new respect to pool and data cache management. JPA scales very well in any manages SP calls transparently by means of ResultSets as environment, no matter if it is used in in-house Intranet a simple SQL statement execution; while in JPA, the that serves hundreds of users or for mission - critical developer needs to do some programming to deal with applications that serve hundreds of thousands of users.
Scalability and applicability: For smaller applications, it could not be necessary to use JPA implementation, since Query Languages supported: JPA implementations as it may increase complexity in applications that has single Hibernate, which uses HQL figure 5 , also supports SQL; database or very few tables; in this case, the developer in this way, JPA implementations give more flexibility to could prefer to go for JDBC plus stored procedures.
But, for Million - user further SQL queries. As a result, for these types of applications JDBC with stored procedures is the best choice.
SQL Languages: Return type Returns entities Returns rows Relational concerns Driven by annotations POJOs The developer must implement it, can be done by simple classes and also by annotations POJOs Database independent Queries are executed by entity manager Change queries depending on the schema Scaling Ease Not ease Stored procedures Can be implemented, but needs some Transparently implemented and used as any other SQL support programming skills statement.
Listing 7. If the class is an inner class, it must be static and should be referenced in the entity class, as in Listing 8.
The code for finding records with a composite primary key is exactly the same as that for finding records with a single primary key. Listing 8. Using an identity class Entity IdClass Customer. Imagine that you want to update a customer record, but, before you update, you want to remove the hyphen from the zip code if one is present. Or say that you want to populate some transient fields after a successful fetch.
JPA provides listeners for these kinds of activities before and after each fetch, insert, or update operation.
The callback methods can be annotated as any of the following: PostLoad PrePersist PostPersist PreUpdate PostUpdate PreRemove PostRemove You can write the callback methods in the entity class itself, or you can write them in a separate class and reference them in the entity class with EntityListeners, as shown in Listing 9.
What if you want to apply class normalization concepts and come up with a separate Address class and refer to that in the Customer entity? After all, an address object could be used with Customer, Employee, Order, or User entities. All you need is an embedded object. You move the address information into a separate class and mark that class as being embeddable, as shown in Listing Refer to this newly created class from the Customer entity with Embedded annotations.
Listing However, they cannot be queried separately. Listing 11 illustrates a sample entity that uses an embedded object. Another non-entity, supplying behavior or non-persistence state. The attributes you inherit from a non- entity are not persisted.
Mapped superclasses, supplying common entity state. Tables in a database have similar fields, but tables are not related to each other. Let's have a look into the various types of inheritance JPA offers. For this scenario, assume that there are two types of customer: a normal customer who buys products from a physical store and an online customer who buys products over the Internet.
Single-table inheritance In single-table inheritance, all the entities in the hierarchy are stored in a single table. Single-table inheritance is the default strategy. Thus, you could omit the Inheritance annotation in the example code in Listing 12 and get the same result. Table 2. This strategy should be reflected in the superclass, as in Listing The OnlineCustomer entity will be a normal entity class that extendsCustomer class, as shown in Listing Persisting objects in single-table inheritance The query in Listing 15 should return you the list of online customers from the data store.
Java Persistence API (JPA)
Fetching only the subclass in single-table inheritance How will it fetch only the online customers? In fact, JPA cannot do this unless you provide it with a hint. That's the significance of the DiscriminatorColumn.
The DiscriminatorValue annotation needs to be provided in the superclass as well as in all the subclasses.
What is ORM?
When you want to fetch online customers, JPA silently queries the data store as in Listing APPT, t0. Table 3. Nothing changes in the way in which you persist and fetch the Customer and OnlineCustomer objects. Table per class inheritance In the table per class inheritance strategy, each class state in a hierarchy is stored in a separate table, as illustrated in Table 4.Lastly, with the launch of the EJB3.
In addition, blogs will be used to keep the community updated on the progress of the JSR. Primarily, my argument is focused on the In the most of cases, the fastest way to get data from a comparison between Java Persistence API and JDBC database is not to execute an enhanced query; the answer Java Database Connectivity , mainly from the is not accessing database often, it means to access cache2: By default, all the fields are of type Basic, which are persisted as-is in the database.
Thus, whenever successful solution at all, because of its complexity in the browser or any other client needs to access development and deployment.
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