java注解之运行时修改字段的注解值操作

public class JavaVo{
@Excel（name = "xxx"）
private String userName;
//省略getset方法
}

ExcelImportUtil.importExcel(file.getInputStream(), configClass(JavaVo.class), params);

 private Class configClass(Class c , String val) {
   
   Field[] fields = c.getDeclaredFields();
   try {
  for(int i = 0;i < fields.length;i++){
  Field f = fields[i];
  Excel excelAn = f.getAnnotation(Excel.class);//Excel是注解类型
  if(excelAn == null){
   continue;
  }
  InvocationHandler h = Proxy.getInvocationHandler(excelAn);
  Field hField = h.getClass().getDeclaredField("memberValues");
    // 因为这个字段事 private final 修饰，所以要打开权限
    hField.setAccessible(true);
    // 获取 memberValues
    Map memberValues = (Map) hField.get(h);
    // 修改 value 属性值 这里修改的是@Excel(name = "姓名")
        //name是key
    memberValues.put("name", val);
  }
 } catch (Exception e) {
  e.printStackTrace();
 }
 return c;
 }

import com.alibaba.fastjson.annotation.JSONField;
import lombok.Data;

@Data
public class A {
  @JSONField(serialize = false)
  private String extendParams;

  @JSONField(serialize = true)
  private String sad;
}

import com.alibaba.fastjson.annotation.JSONField;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
import java.util.Map;
import lombok.val;

/**
 * 动态操作注解属性
 * @since 2020年8月13日20:49:26
 */
public class AnnotationUtils<T> {
  /**
   * 查看注解属性
   * @param t
   * @param name
   * @return
   * @throws NoSuchFieldException
   */
  public Object getJSONFieldProp(T t, String name) throws NoSuchFieldException {
    Field field = t.getClass().getDeclaredField(name);
    JSONField annotation = field.getAnnotation(JSONField.class);
    val serialize = annotation.serialize();
    return serialize;
  }

  /**
   * 修改注解属性
   * @param t
   * @param value
   * @return
   * @throws NoSuchFieldException
   * @throws IllegalAccessException
   */
  public Object setJSONFieldProp(T t,String name, Object value) throws NoSuchFieldException, IllegalAccessException {
    Field field = t.getClass().getDeclaredField(name);
    JSONField annotation = field.getAnnotation(JSONField.class);
    InvocationHandler invocationHandler = Proxy.getInvocationHandler(annotation);
    Field memberValues = invocationHandler.getClass().getDeclaredField("memberValues");
    memberValues.setAccessible(true);
    Map map = (Map) memberValues.get(invocationHandler);
    map.put("serialize",value);
    val serialize = annotation.serialize();
    return serialize;
  }
}

import com.alibaba.fastjson.JSON;

public class TT {

  public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
    AnnotationUtils<A> aAnnotationUtils = new AnnotationUtils<>();
    A a = new A();
    a.setExtendParams("exex");
    a.setSad("sadsad");

    Object extendParams = aAnnotationUtils.getJSONFieldProp(a, "extendParams");//查询注解的值
    System.out.println(extendParams.toString());
//    System.out.println(JSON.toJSONString(a));

    Object extendParams1 = aAnnotationUtils.setJSONFieldProp(a, "extendParams", true);//修改注解的值
    System.out.println(extendParams1.toString());
    System.out.println(JSON.toJSONString(a));
  }
}

false
true
{"extendParams":"exex","sad":"sadsad"}

false
{"sad":"sadsad"}
true
{"sad":"sadsad"}

  public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
    List<A> aList = new ArrayList<>();
    for(int i=0; i<10; i++){
      AnnotationUtils<A> aAnnotationUtils = new AnnotationUtils<>();
      A a = new A();
      a.setExtendParams("exex");
      a.setSad("sadsad");
      if(i%2 == 0) {
        aAnnotationUtils.setJSONFieldProp(a, "extendParams", true);//修改注解的值
      }
      aList.add(a);
    }
    System.out.println(JSON.toJSONString(aList));
  }

[{"extendParams":"exex","sad":"sadsad"},{"extendParams":"exex","sad":"sadsad"},{"extendParams":"exex","sad":"sadsad"},{"extendParams":"exex","sad":"sadsad"},{"extendParams":"exex","sad":"sadsad"},{"extendParams":"exex","sad":"sadsad"},{"extendParams":"exex","sad":"sadsad"},{"extendParams":"exex","sad":"sadsad"},{"extendParams":"exex","sad":"sadsad"},{"extendParams":"exex","sad":"sadsad"}]