在 MySQL DB 中的表更新上刷新 Spring Boot 应用程序中的 bean答案

【问题标题】：Refresh beans in a Spring Boot application on table update in MySQL DB在 MySQL DB 中的表更新上刷新 Spring Boot 应用程序中的 bean
【发布时间】：2021-08-30 22:24:35
【问题描述】：

我的 Spring Boot 应用程序中有一个 bean，如下所示：

@Component
public class DatabaseStudentLoader {

  private final StudentRepository studentRepository;
  private final Map<String, Student>> idToStudentEntityMap;

  /**
   * Instantiates a new Database loader.
   *
   * @param studentRepository the student repository
   */
  public DatabaseStudentLoader(StudentRepository studentRepository) {
    this.studentRepository = studentRepository;
  }

  public void doSomeOperation() {

     //here I am constructing the map, reading entities from DB
    ...
  }

}

在这里，我希望在我的 MySQL 数据库中更新/删除/创建实体后，立即刷新上述 bean。

【问题讨论】：

标签： java mysql spring spring-boot

【解决方案1】：

@乔伊。您可以在 bean 中使用简单的静态属性。

@Component
public class DatabaseStudentLoader {

    // this a static var
    private static Map<String, Student>> idToStudentEntityMap;

    @Value("${some-value-from-spring-if-you-need}")
    private String someValueFromSpringIFYouNeed;

    @PostConstruct
    public void init(){
        // instance map using safely operations
        idToStudentEntityMap = new ConcurrentHashMap<String, Student>();
    }
    
    public void addStudentIntoContext(String key, Student student) {
        // check some roles, if already exists or other logic as you need
        idToStudentEntityMap.put(key, student );
    }
        
    public Student getStudentFromContext(String key) {
        // check some roles, if already exists or other logic as you need
        idToStudentEntityMap.get(key);
    }
    
    // .... all methods about this class
  }

使用 DatabaseStudentLoader 有一个静态参数


  @Service
  public class ServiceUsingDataBase{
  
      @Autowired
      private DatabaseStudentLoader databaseStudentLoader;
      
      public setValueExample(){
        // adding student into static map context that can be used in all application in any time even in updated/deleted/created in my MySQL DB
        databaseStudentLoader.addStudentIntoContext("key", new Student());
      }
      
      public getValueExample(){
        // read student from static map context that can be used in all application in any time
        Student student = databaseStudentLoader.getStudentFromContext("key");
      }
  
  }

【讨论】：