Spring Boot中的JPA查询不返回任何结果

Question

我使用 H2 数据库和一些 JPA 查询创建了一个非常小而简单的 Spring Boot 应用程序。

我的控制器如下：

package me.abhishek.springboot.microservice.example.todo.springbootmicroservicetodoservice;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ThingsToDoController {

    @Autowired
    ThingsToDoRepository repository;

    @GetMapping("/")
    public String index() {
        return "Hello from the ToDo Controller\n";
    }

    @GetMapping("/todo/{name}")
    public ThingsToDo getThingsToDo(@PathVariable String name) {
        ThingsToDo thingToDo=repository.findByNameIgnoreCaseContaining(name);

        return thingToDo;
    }
}

我的豆子如下：

package me.abhishek.springboot.microservice.example.todo.springbootmicroservicetodoservice;

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

@Entity
@Table(name="things_to_do")
public class ThingsToDo {

    @Id
    private Long id;

    @Column(name="name")
    private String name;

    @Column(name="verified")
    private int verificationStatus;

    private String task;

    public ThingsToDo() {

    }

    public ThingsToDo(Long id, String name, int verificationStatus, String task) {
        super();
        this.id=id;
        this.name=name;
        this.verificationStatus=verificationStatus;
        this.task=task;
    }

    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public int getVerificationStatus() {
        return verificationStatus;
    }

    public String getTask() {
        return task;
    }

    @Override
    public String toString() {
        return "ThingsToDo{" + 
                "id=" + id + 
                ", name='" + name + '\'' +
                ", verificationStatus='" + verificationStatus + '\'' +
                '}';
    }
}

H2 数据库架构是：

create table things_to_do
(
    id int,
    name varchar(500),
    verified boolean
);

我运行以将值插入数据库的查询是：

insert into things_to_do (id, name, verified) values (1, 'Hello', 1);
insert into things_to_do (id, name, verified) values (2, 'Bye', 0);

但是，当我访问http://localhost:8080/todo/Hello 时，它不会向我返回任何值；而如果我只是 ping http://localhost:8080，它会输出 Hello from the ToDo Controller。有人可以指出我缺少哪一步吗？谢谢！

编辑：从日志中（不过我不太了解）：

select thingstodo0_.id as id1_0_, thingstodo0_.name as name2_0_, thingstodo0_.task as task3_0_, thingstodo0_.verified as verified4_0_ from things_to_do thingstodo0_ where upper(thingstodo0_.name) like upper(?)
Hibernate: select thingstodo0_.id as id1_0_, thingstodo0_.name as name2_0_, thingstodo0_.task as task3_0_, thingstodo0_.verified as verified4_0_ from things_to_do thingstodo0_ where upper(thingstodo0_.name) like upper(?)
Hibernate: select thingstodo0_.id as id1_0_, thingstodo0_.name as name2_0_, thingstodo0_.task as task3_0_, thingstodo0_.verified as verified4_0_ from things_to_do thingstodo0_ where upper(thingstodo0_.name) like upper(?)
Hibernate: select thingstodo0_.id as id1_0_, thingstodo0_.name as name2_0_, thingstodo0_.task as task3_0_, thingstodo0_.verified as verified4_0_ from things_to_do thingstodo0_ where upper(thingstodo0_.name) like upper(?)
Hibernate: select thingstodo0_.id as id1_0_, thingstodo0_.name as name2_0_, thingstodo0_.task as task3_0_, thingstodo0_.verified as verified4_0_ from things_to_do thingstodo0_ where upper(thingstodo0_.name) like upper(?)
Hibernate: select thingstodo0_.id as id1_0_, thingstodo0_.name as name2_0_, thingstodo0_.task as task3_0_, thingstodo0_.verified as verified4_0_ from things_to_do thingstodo0_ where upper(thingstodo0_.name) like upper(?)
Hibernate: select thingstodo0_.id as id1_0_, thingstodo0_.name as name2_0_, thingstodo0_.task as task3_0_, thingstodo0_.verified as verified4_0_ from things_to_do thingstodo0_ where upper(thingstodo0_.name) like upper(?)
Hibernate: select thingstodo0_.id as id1_0_, thingstodo0_.name as name2_0_, thingstodo0_.task as task3_0_, thingstodo0_.verified as verified4_0_ from things_to_do thingstodo0_ where upper(thingstodo0_.name) like upper(?)

编辑：

ThingsToDoRepository 如下：

package me.abhishek.springboot.microservice.example.todo.springbootmicroservicetodoservice;

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

public interface ThingsToDoRepository extends JpaRepository<ThingsToDo, Long> {
    ThingsToDo findByNameIgnoreCaseContaining(String name);
}

Answer 1

尝试在您的application.properties 文件中将属性spring.jpa.hibernate.ddl-auto 设置为update：

spring.jpa.hibernate.ddl-auto=update

因为H2是一个嵌入式数据库，Spring会自动将spring.jpa.hibernate.ddl-auto的默认值设置为create-drop，这会覆盖你的schema.sql和data.sql。

Spring Boot 会根据你选择一个默认值 它是否认为您的数据库是嵌入式的。它默认为 如果没有检测到模式管理器或根本没有检测到模式管理器，则创建删除 其他情况。

reference

此外，您应该在 ThingsToDoRepository 类的顶部添加 @Repository。