Hello everyone, meet again, I am your friend Quanzhanjun.

Table of contents

  • 1. Add dependencies to pom.xml
  • 2. application.properties add data library configuration
  • 3. Add entity class
  • 4. Add Dao
  • 5. Add Controller
  • 6. Create a new database
  • 7. Test

Part 1 Just two steps! Eclipse+Maven quickly builds the first Spring Boot project A Spring Boot project has been built, and this article is based on this to connect the MySQL database.

1. Add dependencies to pom.xml



2. application.properties add database configuration


spring.jpa.show-sql= true

If the database connection is written as spring.datasource.url= jdbc:mysql://localhost:3306/spring_boot , due to the problem of MySQL version, there may be the following errors, add "?serverTimezone=GMT%2B8" at the back, set the time zone, and solve.

set the driver, spring.datasource.driver-class-name=com.mysql.jdbc.Driver will have the following red warning message. It is said that com.mysql.jdbc.Driver' is deprecated, to use a new driver com.mysql.cj.jdbc.Driver', after changing to `com.mysql.cj.jdbc.Driver' everything works fine.

Loading class com.mysql.jdbc.Driver'. This is deprecated. The new driver class iscom.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

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3. Add entity class

@Entity represents an entity class, @Table(name=”user”) is used to correspond to the use table in the database, @Id is used to express the primary key, and @Column(name=”id”) is used to indicate an id attribute.

@GeneratedValue makes the primary key increment automatically. If you have any questions, please refer to @GeneratedValue source code analysis.

package com.example.demo.domain;

import java.io.Serializable;

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

@Table(name = "user")
public class User implements Serializable {

    private static final long serialVersionUID = 1L;

    private Long id;
    @Column(name = "username")
    private String userName;
    @Column(name = "password")
    private String passWord;

    public User() {

    public User(String userName, String passWord) {
        this.userName = userName;
        this.passWord = passWord;

    public Long getId() {
        return id;

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

    public String getUserName() {
        return userName;

    public void setUserName(String userName) {
        this.userName = userName;

    public String getPassWord() {
        return passWord;

    public void setPassWord(String passWord) {
        this.passWord = passWord;


4. Add Dao

The Dao layer is mainly used to add, delete, check and modify the database. dao only needs to inherit the JpaRepository class, almost no need to write methods, and can automatically generate SQL according to the method name. For example, findByUserName will automatically generate a query method with userName as a parameter.

package com.example.demo.dao;

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

import com.example.demo.domain.User;

public interface UserRepository extends JpaRepository<User, Long> {

    User findByUserName(String userName);


5. Add Controller

package com.example.demo.controller;

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

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import com.example.demo.dao.UserRepository;
import com.example.demo.domain.User;

public class UserController {

    private UserRepository userRepository;

    public List<User> findAll() {
        List<User> list = new ArrayList<User>();
        list = userRepository.findAll();
        return list;

    public User getByUserName(String userName) {
        User user = userRepository.findByUserName(userName);
        return user;


Project structure diagram after adding files to the project:

6. Create a new database

new database mysql://localhost:3306/spring_boot , a required step. Although hibernate will automatically create new tables, the database still needs to be built manually.

Use Navicat to create a new local database, right click on the connection name -> New Database -> Fill in the database information -> OK.

In the user table, insert two test data:

7. Test

Startup project. Send a request with Postman for testing:

http://localhost:8080//user/getAllUser :

http://localhost:8080//user/getByUserName?userName=Turing :

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Posted by cneale on Mon, 12 Sep 2022 21:35:43 +0530