Spring Boot-Spring Data JPA

Spring Data JPA

JPA and Spring Data JPA

Reference: https://blog.csdn.net/cd546566850/article/details/107180272/ Have the most intuitive understanding of JPA and Spring Data JPA through this article

Springboot integrates Spring Data JPA

1. pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.9</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.liwang</groupId>
    <artifactId>jpa</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>jpa</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

2. application.properties

spring.datasource.url=jdbc:mysql:///test2?useUnicode=true &characterEncoding=UTF-8
spring.datasource.username=root
spring.datasource.password=root

# The type of database to use
spring.jpa.database=mysql
spring.jpa.database-platform=mysql
# show sql
spring.jpa.show-sql=true
# When a new field is added to the java entity class, when the application is re-run, the field will be added to the new column in the database table, but the pre-existing column or constraint will not be removed
spring.jpa.hibernate.ddl-auto=update
# Configure the database dialect. By default, the myisam engine is used to create database tables, and the specified dialect is to use the innodb engine
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL8Dialect

3. Create a Book class

@Entity(name = "t_book")
public class Book {<!-- -->

    @Id
    @GeneratedValue(strategy = GenerationType. IDENTITY)
    private Long id;
    private String name;
    private String author;

@Override
    public String toString() {<!-- -->
        return "Book{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", author='" + author + '\'' +
                '}';
    }

    public Long getId() {<!-- -->
        return id;
    }

    public void setId(Long id) {<!-- -->
        this.id = id;
    }

    public String getName() {<!-- -->
        return name;
    }

    public void setName(String name) {<!-- -->
        this.name = name;
    }

    public String getAuthor() {<!-- -->
        return author;
    }

    public void setAuthor(String author) {<!-- -->
        this.author = author;
    }
}

4. At this time, test run project, check whether the book table is generated under the database test2
   
   The operation is successful and the table is created
   
5. Create BookDao interface to implement JpaRepository

public interface BookDao extends JpaRepository<Book, Long> {<!-- -->
}

6. Test save data to database

@SpringBootTest
class JpaApplicationTests {<!-- -->

    @Autowired
    BookDao bookDao;

    @Test
    void contextLoads() {<!-- -->
        Book b = new Book();
        b.setName("Romance of the Three Kingdoms");
        b.setAuthor("Luo Guanzhong");
        bookDao. save(b);
    }

}

Refresh data table

7. Test query, delete, update

 @Test
    void test01() {<!-- -->
        // Query all data, now add multiple records to the database
        List<Book> list = bookDao. findAll();
        System.out.println("list = " + list);

        System.out.println("-------------------");

        // query by id
        Optional<Book> book = bookDao.findById(3L);
        System.out.println("book = " + book);
    }

8. Test pagination

 @Test
    void test03() {<!-- -->
        // Paging query page number starts from 0
        PageRequest pageRequest = PageRequest.of(0, 3, Sort.by(Sort.Order.asc("id")));
        Page<Book> page = bookDao. findAll(pageRequest);
        System.out.println("Total records = " + page.getTotalElements());
        System.out.println("total pages = " + page.getTotalPages());
        System.out.println("Data found = " + page.getContent());
    }

At this point, the simple use of Spring Data Jpa is over. Continue to update the use of custom data operations in the future.

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Website: https://www.fuzm.wang / https://liwangc.gitee.io
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As a beginner, I have not mastered a lot of knowledge, forgive me, please point out any mistakes, in order to improve, thank you! . There will be new learning in the follow-up, and we will continue to add it.