如何通过 Id 从数据库中获取数据 Spring Boot Java REST API

Question

我构建了简单的 REST 服务，我想从基于数据库的 ID 获取数据密钥，但是，当我运行邮递员中没有显示结果时，我该如何解决？

这是我的控制器

    //Get Key

    @RequestMapping(path="/getkey/{company_id}", method = RequestMethod.GET)
    String getKey(@PathVariable int company_id) {
    String encKey = null;



    gkrepo.getKeyByCompanyid(company_id);

    return encKey;


}

这是我的存储库

public interface GenerateKeyRepository extends JpaRepository<KeyEntity, Integer>
{

@Query(value= "SELECT * FROM tb_key", nativeQuery = true)
List<KeyEntity> getAll();

public void getKeyByCompanyid(Integer companyid);


}

Answer 1

您应该按照以下步骤更改存储库中的方法。试试这个。

 public interface GenerateKeyRepository extends JpaRepository<KeyEntity, Integer>
 {

@Query(value= "SELECT * FROM tb_key", nativeQuery = true)
List<KeyEntity> getAll();

public KeyEntity findByCompanyId(Integer companyid);
 }

Answer 2

你的控制器应该是：

@RequestMapping(path="/getkey/{company_id}", method = RequestMethod.GET)
String getKey(@PathVariable int company_id) {
String encKey = null;

KeyEntity keyEntity = gkrepo.getKeyByCompanyid(company_id);

return keyEntity.getKey;

}

你的存储库应该是这样的：

public interface GenerateKeyRepository extends JpaRepository<KeyEntity, Integer>
 {

@Query(value= "SELECT * FROM tb_key", nativeQuery = true)
List<KeyEntity> getAll();

public KeyEntity findByCompanyId(Integer companyid);
 }

Answer 3

您可以尝试按照下面的方式更改方法

public interface GenerateKeyRepository extends JpaRepository<KeyEntity, Integer>
  {

    @Query(value= "SELECT * FROM tb_key", nativeQuery = true)
    List<KeyEntity> getAll();

    public KeyEntity findByCompanyId(Integer companyid);
  }

如果您使用此代码，则必须按以下方式更改代码

gkrepo.findByCompanyId

instead of

gkrepo.getKeyByCompanyid(company_id);

或

public interface GenerateKeyRepository extends JpaRepository<KeyEntity, Integer>
 {

    @Query(value= "SELECT * FROM tb_key", nativeQuery = true)
    List<KeyEntity> getAll();

    @Query(Select k from KeyEntity k where companyid = :companyid)    
    public KeyEntity getKeyByCompanyid(@Param("companyid") Integer companyid);
 }

Answer 4

您正在使用 Spring 数据 JPA。您的存储库接口从扩展的 JpaRepository 接口继承了各种方法。这就是它的全部意义。

https://docs.spring.io/spring-data/jpa/docs/current/api/org/springframework/data/jpa/repository/JpaRepository.html

再无读写查询方法：

@RestController
public class myController{

    @RequestMapping(path="/getkey/{company_id}", method = RequestMethod.GET)
    public KeyEntity getKey(@PathVariable("company_id") int companyId) {

        return gkrepo.findById(companyId); //inherited method
    }

}

此外，如果启用 Spring Data JPA 的 Web 扩展，则根本不需要调用存储库，因为实体将从路径变量中自动解析：

https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#core.web

The DomainClassConverter lets you use domain types in your Spring MVC controller method signatures directly, so that you need not manually lookup the instances through the repository

@RestController
public class myController{

    @RequestMapping(path="/getkey/{company_id}", method = RequestMethod.GET)
    KeyEntity getKey(@PathVariable KeyEntity keyEntity) {

        return keyEntity; 
    }
}

Answer 5

这里的问题是，您忽略了 repository 方法的 return 值和 return null.

@RequestMapping(path="/getkey/{company_id}", method = RequestMethod.GET)
    String getKey(@PathVariable int company_id) {
    String encKey = null;

    gkrepo.findOneByCompanyId(company_id);

    return encKey; //YOU RETURN NULL HERE
}

您需要做的是 return 来自 KeyEntity 对象的密钥。

@RequestMapping(path="/getkey/{company_id}", method = RequestMethod.GET)
    String getKey(@PathVariable int company_id) {

    return gkrepo.getKeyByCompanyid(company_id).getKey();
}

您还需要在 repository 中添加一个方法。

public interface GenerateKeyRepository extends JpaRepository<KeyEntity, Integer> {

    @Query(value= "SELECT * FROM tb_key", nativeQuery = true)
    List<KeyEntity> getAll();

    public void findOneByCompanyId(Integer companyid);
}

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