SpringBoot @SpringBootApplication(exclude={DataSourceAutoConfiguration.calss})注解说明

Posted 2023-04-07 18sui

@SpringBootApplication(exclude=DataSourceAutoConfiguration.calss)

该注解的作用是，排除自动注入数据源的配置，用 exclude 属性进行排除指定的类，在springBoot中使用多数据源时，加上@SpringBootApplication(exclude=DataSourceAutoConfiguration.calss)

DataSourceAutoConfiguration.class 会自动查找 application.yml 或者 properties 文件里的 spring.datasource. 相关属性并自动配置单数据源*

DataSourceAutoConfiguration.class默认会帮我们自动配置单数据源，所以，如果想在项目中使用多数据源就需要排除它，手动指定多数据源。

---

这时springBoot 中的注解是 @SpringBootApplication，数据源中 application.yml为：

spring:

    datasource:

      name: test

        url: jdbc:mysql:/127.0.0.1:3306/test?serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=UTF8

        username: root

        password: root

---

如果springBoot 中要加上 @SpringBootApplication(exclude=DataSourceAutoConfiguration.calss) ，则application.yml 为

spring:

    datasource:

       default：

          name: test

             url: jdbc:mysql:/127.0.0.1:3306/test?serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=UTF8

             username: root

             password: root

SpringBootApp NullPointerException 与 @Autowired 存储库

【中文标题】SpringBootApp NullPointerException 与 @Autowired 存储库

【英文标题】：SpringBootApp NullPointerException with @Autowired repository

【发布时间】：2021-08-24 10:27:01

【问题描述】：

这是我的 Spring Boot 应用程序。 当我运行 main 方法时，总是抛出一个空指针异常。 我不知道为什么 @Autowired JsonReaderService 为空。正如我将其定义为组件。

它是项目 src 文件夹中的子文件夹，因此 Main Method 位于源文件夹之上。那么spring应该正确扫描吧？？

我还有一个测试方法，效果很好。

 @SpringBootApplication
 public class DemoApplication 

@Autowired
private JsonReaderService jsonReaderService;

private static JsonReaderService stat_jsonReaderService;

static Logger logger = LoggerFactory.getLogger(DemoApplication.class);

public static void main(String[] args) throws IOException 

    String textFileName = scanFileName();
    Reader reader = Files.newBufferedReader(Paths.get("src/main/resources/" + textFileName));
    // This line is always null pointer exception. The @autowired Annotation don't work with my JsonReaderService????? WHY
    List<EventDataJson> jsonReaderServicesList = stat_jsonReaderService.readEventDataFromJson(reader);
    stat_jsonReaderService.mappingToDatabase(jsonReaderServicesList);



public static String scanFileName() 
    logger.info("Scanning keyboard input");
    System.out.println("enter a file to scan");
    Scanner scanInput = new Scanner(System.in);
    String text = scanInput.nextLine();
    logger.info("successful keyboard input was : " + text);
    return text;


@PostConstruct
public void init() 
    logger.info("initializing Demo Application");
    stat_jsonReaderService = jsonReaderService;

这里我有一个类，它使用存储库@Autowired 来保存一些实体，但我总是在 repository.save(...) 行中得到一个空指针异常

@Component
public class JsonReaderService 
static Logger logger = LoggerFactory.getLogger(DemoApplication.class);
@Autowired
EventDataRepository repository;
private Reader reader;
private List<EventDataJson> eventDataList;

@Autowired
public JsonReaderService()

public List<EventDataJson> readEventDataFromJson(Reader reader) throws IOException 

    try 
        logger.info("parsing event data from json started");
        Gson gson = new Gson();
        EventDataJson[] eventData = gson.fromJson(reader, EventDataJson[].class);
        eventDataList = Arrays.asList(eventData);
        reader.close();
     catch (IOException e) 
        logger.error("Error while reading the json file");
        e.printStackTrace();
    
    logger.info("parsing json eventData successful finished");
    return eventDataList;


public Boolean mappingToDatabase(List<EventDataJson> eventDataList) 
    logger.info("mapping from json to database eventData started ...");

    Set<String> idList = eventDataList.stream().map(EventDataJson::getId).collect(Collectors.toSet());
    for (String id : idList
    ) 
        Stream<EventDataJson> filteredEventDataList1 = eventDataList.stream().filter((item) -> item.getId().equals(id));
        Stream<EventDataJson> filteredEventDataList0 = eventDataList.stream().filter((item) -> item.getId().equals(id));
        EventDataJson startedEvent = filteredEventDataList1.filter((item) -> item.getState().equals("STARTED")).findAny().orElse(null);
        EventDataJson finishedEvent = filteredEventDataList0.filter((item) -> item.getState().equals("FINISHED")).findAny().orElse(null);
        long duration0 = finishedEvent.getTimestamp() - startedEvent.getTimestamp();
        Boolean alert;
        if (duration0 > 4) 
            alert = true;
         else 
            alert = false;
        
        try 
            this.repository.save(new EventDataDb(id, duration0, startedEvent.getType(), startedEvent.getHost(), alert));
            logger.info("mapping to Database Repository action successful");

         catch (Exception e) 
            logger.error("Exception in database mapping occurred");
            e.printStackTrace();
            return false;

        
    
    return true;

带注释的存储库

@Repository
 public interface EventDataRepository extends JpaRepository<EventDataDb, String> 
 EventDataDb findAllById(String id);
 

测试用例与@autowired Annotation 一起工作得很好我不知道为什么它在 main 方法中不起作用。是因为它是静态的吗？

    @Autowired
       private EventDataRepository repository;

    @Autowired
       private JsonReaderService jReader;
    @Test
    public void whenParseJson_thenTransform_and_save_to_db() throws IOException 
    BufferedReader reader = Files.newBufferedReader(Paths.get("src/main/resources/" + "logfile.txt"));
    List<EventDataJson> eventDataList1 = jReader.readEventDataFromJson(reader);
    if (jReader.mappingToDatabase(eventDataList1)) 
        EventDataDb eventDataFromDb = this.repository.findAllById("scsmbstgra");
        Assertions.assertTrue(eventDataFromDb.getType().equals("APPLICATION_LOG"));
        Assertions.assertTrue(eventDataFromDb.getHost().equals("12345"));
        Assertions.assertTrue(eventDataFromDb.getAlert().equals(true));
        Assertions.assertTrue(eventDataFromDb.getDuration() == 5);
        logger.info("Assert successfully accomplished");
     else
        logger.error("Could not persist eventData to DB Error");

堆栈跟踪

`线程“restartedMain”java.lang.reflect.InvocationTargetException中的异常

at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49)

原因：java.lang.NullPointerException 在 com.creditsuisse.demo.DemoApplication.main(DemoApplication.java:33) ... 5 更多`

【参考方案1】：

您需要运行SpringApplication.run()，因为此方法会启动整个 Spring 框架。由于您的代码中没有它，因此 bean 没有自动装配，并且 JsonReaderService 为空。您可以在Application.java 中执行以下操作。此外，由于这涉及从 CLI 获取输入，为什么不使用 CommandLineRunner，如下所示：

@SpringBootApplication
public class DemoApplication 
  implements CommandLineRunner 

    @Autowired
    private JsonReaderService jsonReaderService;

    public static void main(String[] args) 
        SpringApplication.run(DemoApplication.class, args);
    
 
    @Override
    public void run(String... args) 
        String textFileName = scanFileName();
        Reader reader = Files.newBufferedReader(Paths.get("src/main/resources/" + textFileName));
        List<EventDataJson> jsonReaderServicesList = stat_jsonReaderService.readEventDataFromJson(reader);
        jsonReaderService.mappingToDatabase(jsonReaderServicesList);
    

【讨论】：

感谢您的评论。我添加了行 SpringApplication.run(DemoApplication.class, args);但仍然是相同的异常：线程“restartedMain”org.springframework.boot.devtools.restart.RestartLauncher.run（RestartLauncher.java:49）中的异常原因：java.lang.NullPointerException

您可以将完整的堆栈跟踪添加到问题中吗？

是的，在自动装配的 JsonReaderService 中抛出异常

@edibIsic，我已经用 CommandLineRunner 更新了答案，但没有使用静态。

谢谢伙计。你摇滚！！！现在工作得很好。是因为命令行扫描仪吗？正确的。没有就不会这样做。所以再次感谢。祝您愉快。 :D