Shulou(Shulou.com)06/03 Report--

1 steps for using JPA

JPA=Java Persistence API,Java persistence layer API. JDK5 introduces JPA ORM to simplify Java EE development and integrate ORM technology. JPA defines JPQL (Java Persistence Query Language).

The default integrated JPA Provider for Spring Data JPA is Hibernate.

a. Add JPA dependency in pom.xml

Org.springframework.boot

Spring-boot-starter-data-jpa

b. Then increase the MYSQL dependency:

Mysql

Mysql-connector-java

c. Add the annotation @ Entity before the Model class

@ Entity

Public class user {

d. Add @ Id and @ GeneratedValue tags in the ID field

@ Id

@ GeneratedValue (strategy=GenerationType.AUTO)

Private Integer id

e. Extend the data warehouse interface:

Public interface UserRepository extends CrudRepository {}

f. Add dimensions in front of the control class

@ Controller

@ RequestMapping (path= "/ demo")

Public class UserController {

g. Add annotations in front of the control class repository properties

@ Autowired

Private UserRepository repository

h. Add annotations in and before the operation functions of the control class

@ GetMapping (path = "/ add")

Public @ ResponseBody String addNewUser (@ RequestParam String name, @ RequestParam String email) {

User u = new user ()

U.setName (name)

U.setEmail (email)

Repository.save (u)

Return "Saved"

}

@ Query ("select id,username,sex,address from # {# entityName} u where u.username=:name")

List findUserModel (@ Param ("name") String username)

i. Add dimensions in front of the Application class

@ SpringBootApplication

Public class Application {

Public static void main (String [] args) {

SpringApplication.run (Application.class, args)

}

}

j. Add configuration items to Application.properties

Spring.jpa.hibernate.ddl-auto=create

Spring.datasource.url=jdbc:mysql://localhost:3306/db_example

Spring.datasource.username=springuser

Spring.datasource.password=ThePassword

K. Notes and comments

@ Entity indicates that this class is an entity class and uses the default ORM rule, that is, the class name is the table name in the database table, and the class field name is the field name in the table. If you want to change this default rule, use @ Table to change the mapping rule between the class name and the table name in the database, and @ Column to change the mapping rule between the field name in class and the field name in db.

@ Query this is a way for JPA to support heavyweight queries, and there are two ways: one is JPQL's SQL language, and the other is native SQL language. Common scenarios are as follows:

* like expression:

@ Query (value = "select id,username,sex,address from UserModel b where b.name like%: name%")

List findByNameMatch (@ Param ("name") String name)

* * Native SQL language

@ Query (value = "select * from user b where b.username=?1", nativeQuery = true)

List findByName (String name)

* * use @ Param to annotate the injection parameters

@ Query (value = "select id,username,sex,address from UserModel b where b.username =: name AND b.address=:address AND b.sex=:sex")

List findByNamedParam (@ Param ("name") String name, @ Param ("address") String address, @ Param ("sex") long sex)

* * SPEL expression

@ Query (value = "select * from # {# entityName} b where b.name=?1", nativeQuery = true)

List findByName (String name)

L.JPA frame diagram

M.JPQL syntax

The basic format is as follows:

Select entity alias. Attribute name, entity alias. Property name from entity name as entity alias where entity alias. Entity attribute op comparison value

2 comparison between JPA query method and HQL query statement

Expression.

Query method

Hql query statement

And

FindByLastnameAndFirstname

... Where x.lastname =? 1 and x.firstname =? 2

Or

FindByLastnameOrFirstname

... Where x.lastname =? 1 or x.firstname =? 2

Is,Equals

FindByFirstname,findByFirstnameIs,findByFirstnameEqual

... Where x.firstname = 1?

Between

FindByStartDateBetween

... Where x.startDate between 1? And? 2

LessThan

FindByAgeLessThan

... Where x.age

< ?1 LessThanEqual findByAgeLessThanEqual … where x.age ⇐ ?1 GreaterThan findByAgeGreaterThan … where x.age >

? 1

GreaterThanEqual

FindByAgeGreaterThanEqual

... Where x.age > =? 1

After

FindByStartDateAfter

... Where x.startDate >? 1

Before

FindByStartDateBefore

... Where x.startDate

< ?1 IsNull findByAgeIsNull … where x.age is null IsNotNull,NotNull findByAge(Is)NotNull … where x.age not null Like findByFirstnameLike … where x.firstname like ?1 NotLike findByFirstnameNotLike … where x.firstname not like ?1 StartingWith findByFirstnameStartingWith … where x.firstname like ?1 (parameter bound with appended %) EndingWith findByFirstnameEndingWith … where x.firstname like ?1 (parameter bound with prepended %) Containing findByFirstnameContaining … where x.firstname like ?1 (parameter bound wrapped in %) OrderBy findByAgeOrderByLastnameDesc … where x.age = ?1 order by x.lastname desc Not findByLastnameNot … where x.lastname ?1 In findByAgeIn(Collection ages) … where x.age in ?1 NotIn findByAgeNotIn(Collection age) … where x.age not in ?1 True findByActiveTrue() … where x.active = true False findByActiveFalse() … where x.active = false IgnoreCase findByFirstnameIgnoreCase … where UPPER(x.firstame) = UPPER(?1) 3 MyBatis和Hibernate的区别 SpringBoot都支持mybatis和hibernate，实际上它们都属于ORM框架，整体架构也差不多，如下：

Contrast item

MyBatis

Hibernate

JDBC

Support

Support

JTA transaction

Support

Support

SessionFactoryBuilder

Support

Support

SessionFactory

Support

Support

Session

Support

Support

Development difficulty

The framework is easy to master.

Frame mastery is complex.

SQL statement

Support native SQL for performance optimization

HQL, which generally does not need to write native SQL statements, has low performance.

Caching

Second-level cache is supported. Dirty data may exist.

Support for secondary caching

Portability

Poor

Better

Automation

Semi-automatic

Fully automatic

Security.

Poor

Better

Journal

Poor

Better

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