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This article mainly introduces "why springboot jpaRepository must serialize Entity". In daily operation, I believe that many people have doubts about why springboot jpaRepository must serialize Entity. Xiaobian consulted all kinds of data and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the question of "why springboot jpaRepository must serialize Entity". Next, please follow the editor to study!

Springboot jpaRepository serializes Entity 1. problem

At first, I didn't serialize the entity class Inventory, causing it to directly install the alphabetical sequence to generate the fields of the table Inventory when using the JPA of the embedded database H2.

For example, it turns out that I followed

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

The database imports tables written sequentially, but because there is no serialization, the table structure becomes

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

So later JPA processing failed.

two。 Write a basic use of JpaRepository

By the way, write down the jpa simple restful program based on spring cloud and H2 database.

Entity class 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; @ Entitypublic 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 + "]";}}

The following use JpaRepository to simplify the development process, very comfortable to define a simple service interface, will be automatically implemented, awesome.

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

I put the controller method in the springboot startup class, which is another big problem, because my project can only be forwarded by dispatcher here.

The @ EnableDiscoveryClient here is because I'm doing eureka service discovery for spring cloud, and I need this annotation for the registry to discover the service.

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@RestControllerpublic 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, "hot pot base", 10000, 1, "you eat hot pot, I'll eat bottom"); inventoryRepository.save (new Inventory (2, "micro service architecture", 100,2, "micro service still needs to consider a wave"); return "{Inventory [port:" + port+ ", info: inventory micro service" + "]}" } @ 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)); / / emphasize identity and 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 ()

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