Running mvn clean install deletes data in the database

Question

I'm fairly new at maven spring boot.

I'm running mvn clean install then mvn spring-boot:run I'm then able to go an http post and insert data into the database. I can do an http get and see the data. I can view the data in mysql.

When I re-compile and run mvn clean install again, I'm not sure what's making it delete all the data in my product table in the database.

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>2.7.0</version>
        <relativePath/>
        <!-- lookup parent from repository -->
    </parent>
    <groupId>sample.info</groupId>
    <artifactId>mainapp</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>mainapp</name>
    <description>Spring Boot Project</description>
    <properties>
        <java.version>18</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-rest</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.session</groupId>
            <artifactId>spring-session-core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
    </dependencies>


    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <configuration>
                    <forkCount>0</forkCount>
                    <reuseForks>true</reuseForks>
                    <argLine>-Xmx1024m -XX:MaxPermSize=256m</argLine>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

application.properties

spring.jpa.hibernate.ddl-auto=create
spring.datasource.url=jdbc:mysql://localhost:3306/appdb
spring.datasource.username=root
spring.datasource.password=

server.port = 9095

MainappApplication.java

package sample.info.mainapp;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.config.EnableJpaAuditing; 

@EnableJpaAuditing
@SpringBootApplication
public class MainappApplication {

    public static void main(String[] args) {

        SpringApplication.run(MainappApplication.class, args);
    }

}

controllers/ProductController.java

package sample.info.mainapp.controllers;

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import sample.info.mainapp.model.Product;
import sample.info.mainapp.repository.ProductRepository;

@RestController
@RequestMapping("/api")
public class ProductController {

    @Autowired
    ProductRepository productRepository;

    @GetMapping("/products")
    public List<Product> getAllProducts() {
        final List<Product> productList = new ArrayList<Product>();
        Iterable<Product> iterable = productRepository.findAll();
        iterable.forEach(productList::add);
        return productList;
    }

    @GetMapping("/products/{id}")
    public ResponseEntity<Product> getProductById(@PathVariable(value = "id") Long id) {
        Optional<Product> product = productRepository.findById(id);

        return product.isPresent() ? new ResponseEntity<Product>(product.get(), HttpStatus.OK)
                : new ResponseEntity("No data found", HttpStatus.NOT_FOUND);
    }

    @PostMapping("/products")
    public Product createProduct(@RequestBody Product product) {
        return productRepository.save(product);
    }

    @PutMapping("/products/{id}")
    public ResponseEntity<Product> updateProduct(@PathVariable(value = "id") Long id, @RequestBody Product newProduct) {
        Optional<Product> product = productRepository.findById(id);

        if (product.isPresent()) {
            Product prod = product.get();
            prod.setDescription(newProduct.getDescription());
            prod.setPrice(newProduct.getPrice());
            prod.setTitle(newProduct.getTitle());

            prod = productRepository.save(prod);
            return ResponseEntity.ok().body(prod);
        } else {
            return ResponseEntity.notFound().build();
        }
    }

    @DeleteMapping("/products/{id}")
    public ResponseEntity<Product> deleteProduct(@PathVariable(value = "id") Long id) {
        Optional<Product> product = productRepository.findById(id);

        if (product.isPresent()) {
            productRepository.delete(product.get());
            return new ResponseEntity("Product has been deleted successfully.", HttpStatus.OK);
        } else {
            return ResponseEntity.notFound().build();
        }
    }

}

model/Product.java

package sample.info.mainapp.model;

import javax.persistence.*;
import org.springframework.data.annotation.CreatedDate;
import org.springframework.data.annotation.LastModifiedDate;
import org.springframework.data.jpa.domain.support.AuditingEntityListener;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

import java.util.Date;

@Entity
@Table(name = "products")
@EntityListeners(AuditingEntityListener.class)
@JsonIgnoreProperties(value = { "created_at", "updated_at" }, allowGetters = true)
public class Product {

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

    @Column(name = "description")
    private String description;

    @Column(name = "price")
    private float price;
    
    @Column(nullable = false, updatable = false)
    @Temporal(TemporalType.TIMESTAMP)
    @CreatedDate
    private Date created_at;

    @Column(nullable = false)
    @Temporal(TemporalType.TIMESTAMP)
    @LastModifiedDate
    private Date updated_at;
    
    public Product() {
        
    }
 
    public Product(Long id, String title,  String description, float price) {
        this.id = id;
        this.title = title;
        this.description = description;
        this.price = price;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }

    public Date getCreated_at() {
        return created_at;
    }

    public Date getUpdated_at() {
        return updated_at;
    }
}

repository/ProductRepository.java

package sample.info.mainapp.repository;

import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;

import sample.info.mainapp.model.Product;

@Repository
public interface ProductRepository extends CrudRepository <Product, Long> {
 
}

Answer 1

spring.jpa.hibernate.ddl-auto = create -– Hibernate first drops existing tables, then creates new tables. Click here for more details.

Remove / comment this property from application.properties and try.