jpa java

In the field of object-oriented programming, there are inheritance relationships between classes and classes, such as Java the world needs only extends keyword to determine the parent-child relationship of these two classes, but in the relational database, there are some knowledge correlation relationships. In order to map inheritance to a relational database,Hibernate provides 3 ways to The entire inheritance system is annotated with a sing

1. For LOB types that store big data, JPA can only be annotated in Entiry @lob LOBs represent large object data, including BLOBs and CLOB two types, which are used to store large chunks of binary data, slice data, video data, etc., while the latter is used to store long text data, such as the forum's post content, product details, etc. It is noteworthy that: in different databases, large objects corresponding to the field type is not the same, s

Data uniqueness is a common requirement, but it is dangerous if the framework cannot provide relevant control and the programmer has full control. In JPA, there are the following four policies.A. Automatic container generation --- generatortype. AutoAutomatically Generated by JPAB. Use the automatic growth field of the database to generate --- generationtype. IdentityThe JPA container uses the auto-incremen

Query interface int executeupdate ()Used to execute an UPDATE or DELETE statement.List getresultlist ()Used to execute a SELECT statement and return a list of result set entities.Object Getsingleresult ()3 is used to perform a SELECT statement that returns only a single result entity.Query setfirstresult (int startposition)Used to set which entity record to start returning query results from.Query setmaxresults (int maxresult)Used to set the maximum number of returned result entities. Use it in

) { return NewSpecification() {@Override Publicpredicate topredicate (rootquery, Criteriabuilder CB) {predicate P1=NULL; if(NULL!=parameters) {predicate P2=NULL; for(Integer parameter:parameters) {P2=cb.equal (Root.get (SA), parameter); if(P1! =NULL) {P1=Cb.and (P1, p2); }Else{P1=P2; } } } returnP1; } }; }}Using Java Generics, the basic query method is implemented.The first method in t

1. @Transient@Transient indicates that the property is not a mapping to a field in a database table, and the ORM framework ignores the property;If a property is not a field mapping for a database table, it must be marked as @transient, otherwise the ORM framework defaults to its annotation as @basic;Indicates that the field is not in the database table@Transientpublic int getage () {return;}Jackson Related:2. @JsonIgnorePropertiesThis annotation is a class annotation that, when JSON is serialize

the object. Public InterfaceBookqueryrepositoryexample extends Repository{@Query (value="SELECT * from #{#entityName} b where b.name=?1", Nativequery =true) Listfindbyname (String name);} 6. A more complete example of copying code Public InterfaceBookqueryrepositoryexample extends Repository{@Query (value="SELECT * from book B where B.name=?1", Nativequery =true) List//This method SQL will be error (java.lang.IllegalArgumentException), see the reason, if not see, see the next example@Query (Va

entirely by using it. For performance reasons, this solution is not recommended for production purposes, but can be used for prototyping, testing, and demonstration. When you upgrade from Hibernate 2.1 to 3.0, don't be surprised if you see this error for the first time, because this is the version that hibernate defaults to when lazy initialization is enabled. If you encounter this error or try to resolve it in any other scenario “org.hibernate.LazyInitializationException：无法初始化代理

When developing Java Web applications, we often have to choose the right framework for development to improve efficiency and the quality of the application system. When choosing a frame, the hardest choice is the web framework (the persistence layer framework already has JPA specifications). After using a large number of web frameworks, the actual project (online exam system) needs, I decided to try the l

I. Overview　　Official website: https://projects.spring.io/spring-data-jpa/　　1. What is SPRING-DATA-JPA 　　Spring data JPA, part of the larger Spring data family, makes it easy to easily implement JPA based repositories. This module deals with enhanced support for JPA

Recently, I was working on a web project. I found a small module to take notes and sorted it out a little. Well, I entered the question. The framework used in the entire project is roughly as follows: backend> STRUTS + spring + JPA; Foreground> jggrid The following is the background function logic of the entire project: The following section shows the front-end page: This is the jar package used by the system: Because struts labels are used, you

(). =============================================================================1. How to refer to Entitymanager objectsDepending on the scenario that the entity manager applies to, you can divide it into two types.1) Container-managed EntitymanagerContainer-managed Entitymanager objects must run in the EJB container, not in the Web container and in the Java SE environment. The Entitymanager object in the example in the previous sec

installation package. If you need a good MySQL support Chinese characters (GB2312 encoding), you can choose to download MySQL 5.0 or above version, the installation of the time to select the database character set for GB2312 can. Download, install OpenJPA The latest stable version of OpenJPA is Open JPA 0.97. OpenJPA installation is relatively simple, just want to download the compressed file can be extracted. Let's assume that the downloaded compr

1. What is spring data JPA Spring Data JPA is a set of JPA application frameworks encapsulated by spring based on the ORM Framework, JPA specification, which enables developers to access and manipulate data with minimalist code. It provides common functions including additions and deletions, and is easy to expand. Lea

1. Background of the problem Personally prefer spring data JPA, this time the problem is to use the list type as a field in the entity class, JPA also provides a way to operate, that is, using @elementcollection annotations, the online knowledge of JPA is fragmented, After all, it's not as easy to use as MyBatis. To get to the bottom, take a look at the fields in

Let's look at some common query operations in JPA: //and---are equivalent to the AND keyword in SQL, such as findbyheightandsex (int height,char sex); PublicListintHeightCharsex); //The or---is equivalent to the OR keyword in SQL, such as findbyheightorsex (int height,char sex); PublicListintHeightCharsex); //The between---is equivalent to the between keyword in SQL, such as findbyheightbetween (int min, int max); PublicListintMinintmax); //The Les

Hibernate is one of the most common implementations of JPA, and hiberante itself supports annotation syntax. Now don't look at that heap of XML mappings anymore. And Eclipse also provides tools to generate the entity class directly from the database.I. Project Add JPA toolNow add the existing project to JPA support, first select project right properties->project

Hibernate is one of the most common implementations of JPA, and hiberante itself supports annotation syntax. Now don't look at that heap of XML mappings anymore. And Eclipse also provides tools to generate the entity class directly from the database.I. Project Add JPA toolNow add the existing project to JPA support, first select project right properties->project

What is spring data JPA?SPIRNG Data JPA is a set of simplified JPA development frameworks provided by spring, which, in accordance with the agreed "method naming rules", writes the DAO layer interface, enabling access and manipulation of the database without writing the interface implementation. It also provides a lot of functionality beyond crud, such as paging,

Before we learned how to access a relational database using JPA. The development of our database has been greatly simplified through JPA. However, in the previous example we only mentioned the simplest crud (add-and-remove) operation. In fact, Spring Data JPA has perfect support for paging and sorting queries, and then we'll learn how to use pageable to page thro