为什么 hibernate 不会自动创建表？

Question

I am trying to do a project in Angular but I noticed that the table is not created automatically. I put the structure of the project and the related code to do this. As you can see in mysql, the users_database database is created with the statement "create database", but the employee table is not created.

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>2.4.4</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>net.guides.springboot2</groupId>
    <artifactId>springboot2-jpa-crud-example</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Student_Angular-1</name>
    <description>Rest API for a Simple Employee Management Application</description>
    <properties>
        <java.version>11</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>org.springframework.boot</groupId>
           <artifactId>spring-boot-devtools</artifactId>
           <scope>runtime</scope>
       </dependency>
       <dependency>
           <groupId>mysql</groupId>
           <artifactId>mysql-connector-java</artifactId>
           <scope>runtime</scope>
       </dependency>
       <dependency>
    <groupId>javax.validation</groupId>
    <artifactId>validation-api</artifactId>
    <version>1.0.0.GA</version>
</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>

application.properties

spring.datasource.url = jdbc:mysql://localhost:3306/users_database?useSSL=false
spring.datasource.username = root
spring.datasource.password = root


## Hibernate Properties
# The SQL dialect makes Hibernate generate better SQL for the chosen database
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5InnoDBDialect

# Hibernate ddl auto (create, create-drop, validate, update)
spring.jpa.hibernate.ddl-auto = update

server.servlet.context-path=/springboot-crud-rest

Employee.java

package net.guides.springboot2.springboot2jpacrudexample.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "employees")
public class Employee {

    private long id;
    private String firstName;
    private String lastName;
    private String emailId;
 
    public Employee() {
  
    }
 
    public Employee(String firstName, String lastName, String emailId) {
         this.firstName = firstName;
         this.lastName = lastName;
         this.emailId = emailId;
    }
 
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
        public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
 
    @Column(name = "first_name", nullable = false)
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
 
    @Column(name = "last_name", nullable = false)
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
 
    @Column(name = "email_address", nullable = false)
    public String getEmailId() {
        return emailId;
    }
    public void setEmailId(String emailId) {
        this.emailId = emailId;
    }

    @Override
    public String toString() {
        return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", emailId=" + emailId
       + "]";
    }
 
}

EmployeeRepository.java

package net.guides.springboot2.springboot2jpacrudexample.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import net.guides.springboot2.springboot2jpacrudexample.model.Employee;

@Repository
public interface EmployeeRepository extends JpaRepository<Employee, Long>{

}

EmployeeController.java

package net.guides.springboot2.springboot2jpacrudexample.controller;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired;
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 net.guides.springboot2.springboot2jpacrudexample.exception.ResourceNotFoundException;
import net.guides.springboot2.springboot2jpacrudexample.model.Employee;
import net.guides.springboot2.springboot2jpacrudexample.repository.EmployeeRepository;

@RestController @CrossOrigin(origins = "http://localhost:4200")
@RequestMapping("/api/v1")
public class EmployeeController {
    @Autowired
    private EmployeeRepository employeeRepository;

    @GetMapping("/employees")
    public List<Employee> getAllEmployees() {
        return employeeRepository.findAll();
    }

    @GetMapping("/employees/{id}")
    public ResponseEntity<Employee> getEmployeeById(@PathVariable(value = "id") Long employeeId)
        throws ResourceNotFoundException {
        Employee employee = employeeRepository.findById(employeeId)
          .orElseThrow(() -> new ResourceNotFoundException("Employee not found for this id :: " + employeeId));
        return ResponseEntity.ok().body(employee);
    }
    
    @PostMapping("/employees")
    public Employee createEmployee(@Valid @RequestBody Employee employee) {
        return employeeRepository.save(employee);
    }

    @PutMapping("/employees/{id}")
    public ResponseEntity<Employee> updateEmployee(@PathVariable(value = "id") Long employeeId,
         @Valid @RequestBody Employee employeeDetails) throws ResourceNotFoundException {
        Employee employee = employeeRepository.findById(employeeId)
        .orElseThrow(() -> new ResourceNotFoundException("Employee not found for this id :: " + employeeId));

        employee.setEmailId(employeeDetails.getEmailId());
        employee.setLastName(employeeDetails.getLastName());
        employee.setFirstName(employeeDetails.getFirstName());
        final Employee updatedEmployee = employeeRepository.save(employee);
        return ResponseEntity.ok(updatedEmployee);
    }

    @DeleteMapping("/employees/{id}")
    public Map<String, Boolean> deleteEmployee(@PathVariable(value = "id") Long employeeId)
         throws ResourceNotFoundException {
        Employee employee = employeeRepository.findById(employeeId)
       .orElseThrow(() -> new ResourceNotFoundException("Employee not found for this id :: " + employeeId));

        employeeRepository.delete(employee);
        Map<String, Boolean> response = new HashMap<>();
        response.put("deleted", Boolean.TRUE);
        return response;
    }
}

Answer 1

Try changing your value of hibernate.hbm2ddl.auto to create instead of update

Answer 2

You also need to add the following driver-class-name , platform and generate-dll properties to auto-generate ddl.

Add these properties also.

spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.jpa.database-platform=org.hibernate.dialect.MySQL5InnoDBDialect
spring.jpa.generate-ddl=true