JPA first thing to understand is not a product, it is a norm.
Jpa (Java Persistence API) is a Java Sun Crown persistence specification. It provides an object for Java developers / association mapping tools to manage relational data in Java applications.
It appears mainly to simplify the existing persistence ORM technology development and integration, the end of the current Hibernate, TopLink, JDO and other ORM framework for their own business situation
In pom.xml add references: jpa and mysql
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> </dependency>
Add a database link configuration in the configuration file
when the connection string to specify the format and coding region or will lead to error and Chinese garbled
Then declare an entity class, add annotations to develop @Table table name, @ Entity class that it is an entity Bean
@Id indicated primary keys, @ GeneratedValue indicated primary key type, the figure is an example of the self-energizing primary key mysql
@Column specify the mapping of database column names, the same name, then you can not write
Create an interface inheritance JpaRepository, then we can use our framework for the packaged CURD
Call Interface look at the effect return
Delete the rest of the modifications will not put up all the same.
Next is the JPA queries, JPA will generate a corresponding query based on the method name
The controller layer to try
Call about the interface, perfect return
Delete what is new with this routine, the following is a table
| Keyword | Sample | JPQL snippet |
|---|---|---|
| And | findByLastnameAndFirstname | … where x.lastname = ?1 and x.firstname = ?2 |
| Or | findByLastnameOrFirstname | … where x.lastname = ?1 or x.firstname = ?2 |
| Is,Equals | findByFirstnameIs,findByFirstnameEquals | … 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) |
The next tab is the JPA, JPA comes pagination allows us to directly use
Call Interface returns
Out of the box
The next chapter, we talk about integration Mybaits