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This article introduces the relevant knowledge of "how Springboot generates database tables according to entity classes". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Catalogue

Springboot entity classes generate database tables

Step 1: add springboot-data-jpa and database dependencies

Step 2: write the configuration of the yml file

Step 3: annotations used in entity classes

Step 4: start the project whether to generate a table or not

Step 5: just start the project.

Springboot inherits JPA to generate tables in the database based on entity classes

1. Dependencies added in pom

2. Configure jpa configuration in application.yml

Define user entity classes and map them to tables in the database through annotations

Start the springboot project

Springboot entity classes generate database tables

JPA:springboot-jpa: a series of standard architectures for defining data persistence in databases

The purpose of learning is:

Using springboot to realize the operation of database

Step 1: add springboot-data-jpa and database dependency org.springframework.boot spring-boot-starter-data-jpa mysql mysql-connector-java step 2: write the configuration of the yml file server: port: 8001spring: application: name: jih-manage datasource: name: test url: jdbc:mysql://111.231.231. 56/jih username: root password: root type: com.alibaba.druid.pool.DruidDataSource driver-class-name: com.mysql.jdbc.Driver jpa: hibernate: ddl-auto: update show-sql: true step 3: annotations used in entity classes

Comments on @ Entity entity classes

@ Id maps to attributes of id in the table

@ Gernertervalue adds its self-incrementing attribute

Step 4: start the project whether to generate a table or not

Additional knowledge points:

There are two ways to generate the table configuration file of the database according to the entity class: yml and properties file.

Yml file:

Spring: datasource: driver-class-name: com.mysql.jdbc.Driver url: jdbc:mysql://127.0.0.1:3306/facemap username: root password: root jpa: hibernate: ddl-auto: update show-sql: true

Properties file is written as follows:

Spring.datasource.driver-class-name=com.mysql.jdbc.Driverspring.datasource.url=jdbc:mysql://localhost:3306/dbgirl?characterEncoding=utf8spring.datasource.username=rootspring.datasource.password=rootspring.jpa.show-sql= truespring.jpa.hibernate.ddl-auto=updatespring.jpa.hibernate.dialect=org.hibernate.dialect.MySQL5Dialectspring.jackson.serialization.indent_output=false

Have a more detailed introduction

Reference website:

/ / www.yisu.com/article/222622.htm

How to write an entity class:

Annotations for package com.example.demo;import javax.persistence.Entity;import javax.persistence.GeneratedValue;@Entity / / entity classes public class Girl {@ Id / / @ id Note: select this javax.persistence @ GeneratedValue private Integer id; private String cupSize; private Integer age; public Girl () {} public Integer getId () {return id;} public void setId (Integer id) {this.id = id } public String getCupSize () {return cupSize;} public void setCupSize (String cupSize) {this.cupSize = cupSize;} public Integer getAge () {return age;} public void setAge (Integer age) {this.age = age;}} step 5: start the project

Complete ~

Springboot inherits JPA to generate tables in the database based on entity classes

First, build the springboot framework. After the construction is completed:

1. Dependency org.springframework.boot spring-boot-starter-data-jdbc org.springframework.boot spring-boot-starter-web org.mybatis.spring.boot mybatis-spring-boot-starter 2.1.1 added in pom Org.springframework.boot spring-boot-starter-data-jpa mysql mysql-connector-java 8.0.15 org.projectlombok lombok true org.springframework.boot spring-boot-starter-test Test org.junit.vintage junit-vintage-engine 2. configure jpa configuration in application.yml server: port: 8080 spring: datasource: type: com.zaxxer.hikari.HikariDataSource driver-class-name: com.mysql.cj.jdbc.Driver url: jdbc : mysql://localhost:3306/h6mall?useUnicode=true&characterEncoding=utf-8&useSSL=false username: root password: 123456 hikari: minimum-idle: 5 idle-timeout: 180000 maximum-pool-size: 10 auto-commit: true pool-name: MyHikariCP connection-timeout: 30000 jpa: hibernate: ddl-auto: update show-sql: true

The value of jpa.hibernate.ddl-auto attribute under jpa is as follows:

Ddl-auto:create (every time you run the program, no form will be created and the data in the table will be emptied)

Ddl-auto:create-drop (empties the table every time the program ends)

Ddl-auto:update (every time you run the program, no form will be created, and the data in the table will not be emptied, but will only be updated)

Ddl-auto:validate (the running program will verify whether the data is the same as the field type of the database, and different will report an error)

In general, choose update and use other attribute values with caution.

Define the user entity class and map the table import javax.persistence.*; @ Entity@Table (name = "user") @ Datapublic class User {@ Id @ GeneratedValue private Long id; / / name attribute in the database to the field name of the table through annotations. Length is the length of the field @ Column (length = 30, name = "userId") private String userId; @ Column (name = "userName", length = 20, columnDefinition= "varchar (100) COMMENT 'username") private String userName; @ Column (name = "phone", length = 20) private String phone; @ Column (name = "password", length = 30) private String password; @ Column (name = "userRealName", length = 20) private String userRealName @ Column (name = "address", length = 20) private String address;} start the springboot project

You can see that the console shows the

Then check to see if the corresponding table is generated in the database:

This is the end of "how Springboot generates database tables based on entity classes". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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