通过反射调用吸气剂的最佳方式

4 回答

• 2

  我认为这应该指向正确的方向：

  import java.beans.*
  
  for (PropertyDescriptor pd : Introspector.getBeanInfo(Foo.class).getPropertyDescriptors()) {
    if (pd.getReadMethod() != null && !"class".equals(pd.getName()))
      System.out.println(pd.getReadMethod().invoke(foo));
  }
  

  请注意，您可以自己创建BeanInfo或PropertyDescriptor实例，即不使用Introspector . 但是，Introspector在内部进行一些缓存，这通常是一件好事（tm） . 如果你没有缓存感到高兴，你甚至可以去寻找

  // TODO check for non-existing readMethod
  Object value = new PropertyDescriptor("name", Person.class).getReadMethod().invoke(person);
  

  但是，有很多库可以扩展和简化java.beans API . Commons BeanUtils是一个众所周知的例子 . 在那里，你只需：

  Object value = PropertyUtils.getProperty(person, "name");
  

  BeanUtils附带其他方便的东西 . 即，即时值转换（对象到字符串，字符串到对象），以简化用户输入的设置属性 .

  回复于 2024-04-26T13:13:34+08:00
• 4

  您可以使用Reflections框架

  import static org.reflections.ReflectionUtils.*;
  Set<Method> getters = ReflectionUtils.getAllMethods(someClass,
        withModifier(Modifier.PUBLIC), withPrefix("get"), withAnnotation(annotation));
  

  回复于 2024-04-26T13:13:34+08:00
• 210

  命名约定是成熟的JavaBeans规范的一部分，并受java.beans包中的类支持 .

  回复于 2024-04-26T13:13:34+08:00
• 16

  您可以调用反射，还可以通过注释为getter设置序列顺序

  public class Student {
  
  private String grade;
  
  private String name;
  
  private String id;
  
  private String gender;
  
  private Method[] methods;
  
  @Retention(RetentionPolicy.RUNTIME)
  public @interface Order {
      int value();
  }
  
  /**
   * Sort methods as per Order Annotations
   * 
   * @return
   */
  private void sortMethods() {
  
      methods = Student.class.getMethods();
  
      Arrays.sort(methods, new Comparator<Method>() {
          public int compare(Method o1, Method o2) {
              Order or1 = o1.getAnnotation(Order.class);
              Order or2 = o2.getAnnotation(Order.class);
              if (or1 != null && or2 != null) {
                  return or1.value() - or2.value();
              }
              else if (or1 != null && or2 == null) {
                  return -1;
              }
              else if (or1 == null && or2 != null) {
                  return 1;
              }
              return o1.getName().compareTo(o2.getName());
          }
      });
  }
  
  /**
   * Read Elements
   * 
   * @return
   */
  public void readElements() {
      int pos = 0;
      /**
       * Sort Methods
       */
      if (methods == null) {
          sortMethods();
      }
      for (Method method : methods) {
          String name = method.getName();
          if (name.startsWith("get") && !name.equalsIgnoreCase("getClass")) {
              pos++;
              String value = "";
              try {
                  value = (String) method.invoke(this);
              }
              catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
                  e.printStackTrace();
              }
              System.out.println(name + " Pos: " + pos + " Value: " + value);
          }
      }
  }
  
  // /////////////////////// Getter and Setter Methods
  
  /**
   * @param grade
   * @param name
   * @param id
   * @param gender
   */
  public Student(String grade, String name, String id, String gender) {
      super();
      this.grade = grade;
      this.name = name;
      this.id = id;
      this.gender = gender;
  }
  
  /**
   * @return the grade
   */
  @Order(value = 4)
  public String getGrade() {
      return grade;
  }
  
  /**
   * @param grade the grade to set
   */
  public void setGrade(String grade) {
      this.grade = grade;
  }
  
  /**
   * @return the name
   */
  @Order(value = 2)
  public String getName() {
      return name;
  }
  
  /**
   * @param name the name to set
   */
  public void setName(String name) {
      this.name = name;
  }
  
  /**
   * @return the id
   */
  @Order(value = 1)
  public String getId() {
      return id;
  }
  
  /**
   * @param id the id to set
   */
  public void setId(String id) {
      this.id = id;
  }
  
  /**
   * @return the gender
   */
  @Order(value = 3)
  public String getGender() {
      return gender;
  }
  
  /**
   * @param gender the gender to set
   */
  public void setGender(String gender) {
      this.gender = gender;
  }
  
  /**
   * Main
   * 
   * @param args
   * @throws IOException
   * @throws SQLException
   * @throws InvocationTargetException
   * @throws IllegalArgumentException
   * @throws IllegalAccessException
   */
  public static void main(String args[]) throws IOException, SQLException, IllegalAccessException,
          IllegalArgumentException, InvocationTargetException {
      Student student = new Student("A", "Anand", "001", "Male");
      student.readElements();
  }
  

  }

  排序时的输出

  getId Pos: 1 Value: 001
  getName Pos: 2 Value: Anand
  getGender Pos: 3 Value: Male
  getGrade Pos: 4 Value: A
  

  回复于 2024-04-26T13:13:34+08:00