尽管出现 FileNotFoundException，Java Spring Boot 配置文件仍能正确处理

Question

FileNotFoundException for owners.json 文件，尽管在 mvn clean install 和/或 mvn spring-boot:run 期间读取并填充数据库>但是java -jar ./target/car-api-0.0.1-SNAPSHOT.jar。

使用 Java 1.8、Spring Boot、JPA，我创建了一个 Spring Boot 微服务，在微服务启动期间从文件加载 json 数据:

<小时/>

@Component
public class DataInserter implements ApplicationListener<ContextRefreshedEvent> {

    @Value("classpath:data/owners.json")
    Resource ownersResource;

    @Value("classpath:data/cars.json")
    Resource carsResource;

    @Autowired
    private OwnerService ownerService;

    @Autowired
    private CarsService carService;

    @Override
    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
        List<Owner> populatedOwners = new ArrayList<>();
        try {
            Owner aOwner;

            File ownersFile = ownersResource.getFile();
            File carsFile = carsResource.getFile();

            String ownersString = new String(Files.readAllBytes(ownersFile.toPath()));
            String carsString = new String(Files.readAllBytes(carsFile.toPath()));

            ObjectMapper mapper = new ObjectMapper();
            List<Owner> owners = Arrays.asList(mapper.readValue(ownersString, Owner[].class));
            List<Cars> cars = Arrays.asList(mapper.readValue(carsString, ElectricCars[].class));

            // Populate owners one by one
            for (Owner owner : owners) {
                aOwner = new Owner(owner.getName());
                ownerService.createOwner(aOwner);
                populatedOwners.add(aOwner);
            }

            // Populate owner cars one by one
            for (int i = 0; i < populatedOwners.size(); i++) {
                carService.createCars(populatedOwners.get(i).getId(), cars.get(i));
            }

        }
        catch(IOException ioe) {
            ioe.printStackTrace();;
        }
    }
}

<小时/>

src/main/resources/data/cars.json:

[
  {
      "make": "Honda",
      "model": "Accord",
      "year": "2020"
  },
  {
      "make": "Nissan",
      "model": "Maxima",
      "year": "2019"
  },
  {
      "make": "Toyota",
      "model": "Prius",
      "year": "2015"
  },
  {
      "make": "Porsche",
      "model": "911",
      "year": "2017"
  },
  {
      "make": "Hyundai",
      "model": "Elantra",
      "year": "2018"
  },
  {
      "make": "Volkswagen",
      "model": "Beatle",
      "year": "1973"
  },
  {
      "make": "Ford",
      "model": "F-150",
      "year": "2010"
  },
  {
      "make": "Chevrolet",
      "model": "Silverado",
      "year": "2020"
  },
  {
      "make": "Toyota",
      "model": "Camary",
      "year": "2018"
  },
  {
      "make": "Alfa",
      "model": "Romeo",
      "year": "2017"
  }
]

<小时/>

src/main/resources/data/owners.json:

[
  {
    "name": "Tom Brady"
  },
  {
    "name": "Kobe Bryant"
  },
  {
    "name": "Mike Tyson"
  },
  {
    "name": "Scottie Pippen"
  },
  {
    "name": "John Madden"
  },
  {
    "name": "Arnold Palmer"
  },
  {
    "name": "Tiger Woods"
  },
  {
    "name": "Magic Johnson"
  },
  {
    "name": "George Foreman"
  },
  {
    "name": "Charles Barkley"
  }

]

<小时/>

所以，当我运行这个时:

mvn clean install

一切正常!

但是当我随后这样做时:

java -jar ./target/car-api-0.0.1-SNAPSHOT.jar

我在 IntelliJ IDEA 的标准输出中看到了这一点:

java.io.FileNotFoundException: class path resource [data/owners.json] cannot be resolved to absolute file path because it does not reside in the file system: jar:file:/Owners/myowner/car-api/target/car-api-0.0.1-SNAPSHOT.jar!/BOOT-INF/classes!/data/owners.json
    at org.springframework.util.ResourceUtils.getFile(ResourceUtils.java:217)
    at org.springframework.core.io.AbstractFileResolvingResource.getFile(AbstractFileResolvingResource.java:154)
    at com.myapi.bootstrap.DataInserter.onApplicationEvent(DataInserter.java:50)
    at com.myapi.bootstrap.DataInserter.onApplicationEvent(DataInserter.java:24)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
    at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:403)
    at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:360)
    at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:897)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.finishRefresh(ServletWebServerApplicationContext.java:162)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:553)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215)
    at com.nuvve.CarApplication.main(CarApplication.java:12)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:51)
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:52)

<小时/>

现在，数据库仍为空，我无法通过任何 HTTP Get 请求访问我的数据。

<小时/>

pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.myapi</groupId>
    <artifactId>car-api</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>car-api</name>
    <description>Car REST API</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jdbc</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

<小时/>

src/main/resources/applications.properties:

server.servlet.context-path=/car-api
server.port=8080
server.error.whitelabel.enabled=false

# Database specific
spring.jpa.hibernate.ddl-auto=create
spring.datasource.url=jdbc:mysql://localhost:3306/car_db?useSSL=false
spring.datasource.ownername=root
spring.datasource.password=

<小时/>

所有者实体:

@Entity
@Table(name = "owner")
public class Owner {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotNull
    private String name;


    @OneToMany(cascade = CascadeType.ALL,
                fetch = FetchType.EAGER,
                mappedBy = "owner")
    private List<Car> cars = new ArrayList<>();

    public Owner() {
    }

    // Getter & Setters omitted for brevity.
}

汽车实体:

@Entity
@Table(name="car")
public class Car {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    String make;
    String model;
    String year;

    @JsonIgnore
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "owner_id", nullable = false)
    private Owner owner;

    // Getter & Setters omitted for brevity.
}

<小时/>

所有者存储库:

@Repository
public interface OwnerRepository extends JpaRepository<Owner, Long> {
}

<小时/>

汽车存储库:

@Repository
public interface CarRepository extends JpaRepository<Car, Long> {
}

<小时/>

所有者服务:

public interface OwnerService {

    boolean createOwner(Owner owner);

    Owner getOwnerByOwnerId(Long ownerId);

    List<Owner> getAllOwners();

}

<小时/>

OwnerServiceImpl:

@Service
public class OwnerServiceImpl implements OwnerService {


    @Autowired
    OwnerRepository ownerRepository;

    @Autowired
    CarRepository carRepository;

    @Override
    public List<Owner> getAllOwners() {
        return ownerRepository.findAll();
    }

    @Override
    public boolean createOwner(Owner owner) {
        boolean created = false;
        if (owner != null) {
            ownerRepository.save(owner);
            created = true;
        }
        return created;
    }

    @Override
    public Owner getOwnerByOwnerId(Long ownerId) {
        Optional<Owner> owner = null;
        if (ownerRepository.existsById(ownerId)) {
            owner = ownerRepository.findById(ownerId);
        }
        return owner.get();
    }
}

<小时/>

汽车服务:

public interface CarService {

    boolean createCar(Long ownerId, Car car);
}

<小时/>

CarServiceImpl:

@Service
public class CarServiceImpl implements CarService {

    @Autowired
    OwnerRepository ownerRepository;

    @Autowired
    CarRepository carRepository;

    @Override
    public boolean createCar(Long ownerId, Car car) {
        boolean created = false;
        if (ownerRepository.existsById(ownerId)) {
            Optional<Owner> owner = ownerRepository.findById(ownerId);
            if (owner != null) {
                List<Car> cars = owner.get().getCars();
                cars.add(car);
                owner.get().setCars(cars);
                car.setOwner(owner.get());
                carRepository.save(car);
                created = true;
            }
        }
        return created;
    }

}

<小时/>

所有者 Controller :

@RestController
public class OwnerController {


    private HttpHeaders headers = null;

    @Autowired
    OwnerService ownerService;

    public OwnerController() {
        headers = new HttpHeaders();
        headers.add("Content-Type", "application/json");
    }

    @RequestMapping(value = { "/owners" }, method = RequestMethod.POST, produces = "APPLICATION/JSON")
    public ResponseEntity<Object> createOwner(@Valid @RequestBody Owner owner) {
        boolean isCreated = ownerService.createOwner(owner);
        if (isCreated) {
            return new ResponseEntity<Object>(headers, HttpStatus.OK);
        }
        else {
            return new ResponseEntity<Object>(HttpStatus.NOT_FOUND);
        }
    }


    @RequestMapping(value = { "/owners" }, method = RequestMethod.GET, produces = "APPLICATION/JSON")
    public ResponseEntity<Object> getAllOwners() {
        List<Owner> owners = ownerService.getAllOwners();

        if (owners.isEmpty()) {
            return new ResponseEntity<Object>(HttpStatus.NOT_FOUND);
        }
        return new ResponseEntity<Object>(owners, headers, HttpStatus.OK);
    }


    @RequestMapping(value = { "/owners/{ownerId}" }, method = RequestMethod.GET, produces = "APPLICATION/JSON")
    public ResponseEntity<Object> getOwnerByOwnerId(@PathVariable Long ownerId) {
        if (null == ownerId || "".equals(ownerId)) {
            return new ResponseEntity<Object>(HttpStatus.NOT_FOUND);
        }
        Owner owner = ownerService.getOwnerByOwnerId(ownerId);
        return new ResponseEntity<Object>(owner, headers, HttpStatus.OK);
    }

}

<小时/>

汽车 Controller :

@RestController
public class CarController {

    private HttpHeaders headers = null;

    @Autowired
    CarService carService;

    public CarController() {
        headers = new HttpHeaders();
        headers.add("Content-Type", "application/json");
    }

    @RequestMapping(value = { "/cars/{ownerId}" }, method = RequestMethod.POST, produces = "APPLICATION/JSON")
    public ResponseEntity<Object> createCarBasedOnOwnerId(@Valid @RequestBody Car car, Long ownerId) {
        boolean isCreated = carService.createCar(ownerId, car);
        if (isCreated) {
            return new ResponseEntity<Object>(headers, HttpStatus.OK);
        }
        else {
            return new ResponseEntity<Object>(HttpStatus.NOT_FOUND);
        }
    }

<小时/>

为什么在发出 mvn clean install 和/或 mvn spring-boot:run 时正确填充数据库但抛出此 FileNotFoundException？

它必须与 java -jar ./target/car-api-0.0.1-SNAPSHOT.jar 一起使用，因为这是运行 JUnit 测试并设置服务的唯一方法Linux/Unix 上的守护进程(临时和生产服务器)。

Answer 1

它不起作用，因为 Owners.json 文件嵌入在 Spring Boot jar 内，并且 jar 没有扩展:

 jar:file:/Owners/myowner/car-api/target/car-api-0.0.1-SNAPSHOT.jar!/BOOT-INF/classes!/data/owners.json
    at org.springframework.util.ResourceUtils.getFile(ResourceUtils.java:217)
    at org.springframework.core.io.AbstractFileResolvingResource.getFile(AbstractFileResolvingResource.java:154)

<小时/>

我提出的解决方法是将 json 数据文件外部化到外部目录中。

<小时/>

src/main/application.properties:

owners.datafile=/ext/car-api/owners.json
cars.datafile=/ext/car-api/cars.json

<小时/>

@Component
public class DataInserter implements ApplicationListener<ContextRefreshedEvent> {


    @Value("${owners.datafile}")
    File ownersFile;

    @Value("${cars.datafile}")
    File carsFile;

    @Autowired
    private OwnerService ownerService;

    @Autowired
    private CarsService carService;

    @Override
    public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
        List<Owner> populatedOwners = new ArrayList<>();
        try {
            Owner aOwner;

            String ownersString = new String(Files.readAllBytes(ownersFile.toPath()));
            String carsString = new String(Files.readAllBytes(carsFile.toPath()));

            ObjectMapper mapper = new ObjectMapper();
            List<Owner> owners = Arrays.asList(mapper.readValue(ownersString, Owner[].class));
            List<Car> cars = Arrays.asList(mapper.readValue(carsString, Cars[].class));

            // Populate owners one by one
            for (Owner owner : owners) {
                aOwner = new Owner(owner.getName());
                ownerService.createOwner(aOwner);
                populatedOwners.add(aOwner);
            }

            // Populate owner cars one by one
            for (int i = 0; i < populatedOwners.size(); i++) {
                carService.createCars(populatedOwners.get(i).getId(), cars.get(i));
            }

        }
        catch(IOException ioe) {
            ioe.printStackTrace();;
        }
    }
}