springboot jpaRepository為何一定要對(duì)Entity序列化

更新時(shí)間：2021年12月06日 14:55:43 作者：Interesting_Talent

這篇文章主要介紹了springboot jpaRepository為何一定要對(duì)Entity序列化，具有很好的參考價(jià)值，希望對(duì)大家有所幫助。如有錯(cuò)誤或未考慮完全的地方，望不吝賜教

springboot jpaRepository對(duì)Entity序列化

1. 問題

一開始，我沒有對(duì)實(shí)體類Inventory序列化，導(dǎo)致在使用內(nèi)嵌數(shù)據(jù)庫H2的JPA時(shí)，它直接安裝字母序列把表Inventory的字段生成。

舉例，原來我按照

inventory(id, name, quantity, type, comment)

順序?qū)懙臄?shù)據(jù)庫導(dǎo)入表，但是因?yàn)闆]有序列化，導(dǎo)致表結(jié)構(gòu)變成

inventory(id, comment，name, quantity, type )

所以后面JPA處理失敗。

2. 寫個(gè)基本的JpaRepository的使用

順便記錄一下寫spring cloud 基于和H2 database的jpa簡單restful 程序。

實(shí)體類Inventory

package com.example.demo; 
import java.io.Serializable; 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
 
@Entity
public class Inventory implements Serializable{ 
    private static final long serialVersionUID = 1L; 
    @Id
    @SequenceGenerator(name="inventory_generator", sequenceName="inventory_sequence", initialValue = 2)
    @GeneratedValue(generator = "inventory_generator")
    private Integer id;
    @Column(nullable = false)
    private String name;
    @Column(nullable = false)
    private Integer quantity;
    @Column(nullable = false)
    private Integer type;
    @Column(nullable = false)
    private String comment;
    public Inventory(Integer id, String name, Integer quantity, Integer type, String comment) {
        super();
        this.id = id;
        this.name = name;
        this.quantity = quantity;
        this.type = type;
        this.comment = comment;
    }
    public Inventory() {
        super();
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getQuantity() {
        return quantity;
    }
    public void setQuantity(Integer quantity) {
        this.quantity = quantity;
    }
    public Integer getType() {
        return type;
    }
    public void setType(Integer type) {
        this.type = type;
    }
    public String getComment() {
        return comment;
    }
    public void setComment(String comment) {
        this.comment = comment;
    }
    @Override
    public String toString() {
        return "Inventory [id=" + id + ", name=" + name + ", quantity=" + quantity + ", type=" + type + ", comment="
                + comment + "]";
    }
}

下面使用JpaRepository簡化開發(fā)流程，非常舒服地定義簡單的service 接口即可，會(huì)自動(dòng)實(shí)現(xiàn)，大贊。

package com.example.demo; 
import org.springframework.data.jpa.repository.JpaRepository; 
public interface InventoryRepository extends JpaRepository<Inventory, Integer> { 
    Inventory findById(Integer id); 
}

我把controller方法放到了springboot啟動(dòng)類里面，這又是一個(gè)大問題，因?yàn)槲业捻?xiàng)目只有放在這才能被dispatcher轉(zhuǎn)發(fā)，簡直了。

這里的@EnableDiscoveryClient 是因?yàn)槲以谧鰏pring cloud的eureka 服務(wù)發(fā)現(xiàn)，需要這個(gè)注解讓注冊中心發(fā)現(xiàn)這個(gè)服務(wù)。

package com.example.demo; 
import java.time.LocalTime; 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
 
@SpringBootApplication
@EnableDiscoveryClient
@RestController
public class InventoryApplication { 
    public static void main(String[] args) {
        SpringApplication.run(InventoryApplication.class, args);
    }
    @Autowired
    private InventoryRepository inventoryRepository;
 
    @Value("${server.port}")
    private Integer port; 
    @RequestMapping("/info")
    public String info(){
        inventoryRepository.save(new Inventory(1, "火鍋底料", 10000, 1, "你吃火鍋，我吃底料"));
        inventoryRepository.save(new Inventory(2, "微服務(wù)架構(gòu)", 100, 2, "微服務(wù)還是要考慮 一波"));
        return "{Inventory[port:"+port+", info:庫存微服務(wù)"+"]}";
    }
 
    @GetMapping("/get/{id}")
    @ResponseBody
    @Transactional
    public String getById(@PathVariable("id")Integer id){
        return inventoryRepository.findById(id).toString();
    }
 
    @GetMapping("/")
    @ResponseBody
    @Transactional
    public String re(){
        return inventoryRepository.findAll().toString();
    }
 
    @GetMapping("/delete/{id}")
    @ResponseBody
    @Transactional
    public String delete(@PathVariable("id")Integer id){
        inventoryRepository.delete(id);
        return "delete successfully";
    }
 
    @GetMapping("/save/id={id}&name={name}&quantity={quantity}&type={type}&comment={comment}")
/*  @ResponseBody
    @Transactional*/
    public String save(@PathVariable("id")Integer id,@PathVariable("name")String name,
            @PathVariable("quantity")Integer quantity,@PathVariable("type")Integer type,
            @PathVariable("comment")String comment){
        inventoryRepository.save(new Inventory(id,name,quantity,type,comment));
        System.out.println(new Inventory(id,name,quantity,type,comment));
        //強(qiáng)調(diào)一下identity和auto
        return "save successfully";
    }
 
    @GetMapping("/update/id={id}&name={name}&quantity={quantity}&type={type}&comment={comment}")
    @ResponseBody
    @Transactional
    public String update(@PathVariable("id")Integer id,@PathVariable("name")String name,
            @PathVariable("quantity")Integer quantity,@PathVariable("type")Integer type,
            @PathVariable("comment")String comment){
        Inventory inventory=inventoryRepository.findById(id);
        if(inventory.getComment().length()<LocalTime.now().toString().length()){
            inventory.setComment(inventory.getComment()+LocalTime.now());
        }else{
            inventory.setComment(inventory.getComment().substring(0,inventory.getComment().length()-
                    LocalTime.now().toString().length())+LocalTime.now());
        }
        inventoryRepository.save(inventory);
        inventoryRepository.flush();
        return "update successfully";
    }
}

application.properties的配置很關(guān)鍵，搜了不少教程。

spring.jpa.show-sql=true
logging.pattern.level=trace
server.port=8765
spring.application.name=inventory
server.tomcat.max-threads=1000
eureka.instance.leaseRenewalIntervalInSeconds= 10
eureka.client.registryFetchIntervalSeconds= 5
eureka.client.serviceUrl.defaultZone=http://localhost:8889/eureka
#eureka.client.service-url.defaultZone=http://${eureka.instance.hostname}:${eureka.instance.server.port}/eureka
 
#spring.thymeleaf.prefix=classpath:/templates/  
#spring.thymeleaf.suffix=.html  
#spring.thymeleaf.mode=HTML5  
#spring.thymeleaf.encoding=UTF-8  
# ;charset=<encoding> is added  
#spring.thymeleaf.content-type=text/html  
# set to false for hot refresh  
spring.h2.console.enabled=true
spring.thymeleaf.cache=false  
spring.jpa.hibernate.ddl-auto=update
#這里是把h2持久化到本地文件夾，這可以保持?jǐn)?shù)據(jù)
spring.datasource.url=jdbc:h2:file:C\:/h2/h2cache;AUTO_SERVER=TRUE;DB_CLOSE_DELAY=-1
logging.file=c\:/h2/logging.log
logging.level.org.hibernate=debug
#spring.datasource.data=classpath:import.sql

數(shù)據(jù)庫是自動(dòng)導(dǎo)入的，只要命名方式是import.sql, 放在src/main/resources下面就可以

insert into inventory(id, name, quantity, type, comment) values (1, "火鍋底料", 10000, 1, "你吃火鍋，我吃底料")
insert into inventory(id, name, quantity, type, comment) values (2, "微服務(wù)架構(gòu)", 100, 2, "微服務(wù)還是要考慮 一波")

最后一個(gè)簡單的測試

junit測試一波

package com.example.demo; 
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner; 
@RunWith(SpringRunner.class)
@SpringBootTest
public class InventoryApplicationTests {
 
    @Autowired
    private InventoryRepository inventoriRepository;
 
    @Test
    public void test2() {
        System.out.println(inventoriRepository.findAll());
    } 
}

這里寫圖片描述

上圖是項(xiàng)目結(jié)構(gòu)圖

springboot 使用JpaRepository

在對(duì)數(shù)據(jù)庫操作時(shí)使用 MissionInfoRepository，對(duì)應(yīng)的實(shí)體類必須用下面兩個(gè)注解修飾

@Entity
@Table(name = "mission_info")

主鍵用下面修飾

 @Id
 @GeneratedValue(strategy = IDENTITY)
 @Column(name = "id", nullable = false)

在這里插入圖片描述

屬性命名如果使用駝峰，例如missionId,表中字段對(duì)應(yīng)mission_id,否則對(duì)數(shù)據(jù)庫操作的時(shí)候會(huì)報(bào)錯(cuò)，所以在表字段定義的時(shí)候，方便代碼里使用JPA的話，表字段定義多個(gè)詞之間用“_”隔開，而不是駝峰定義表字段。

以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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