自定义注解

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Documented
@Inherited
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface ISEmptyAnnotation {
    public boolean isEmpty() default true;
    public String message() default "字段不能为空！";
}

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Documented
@Inherited
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MaxSize {
    public int max() default 20;
    
     public String message() deault "长度太长";
}

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Documented
@Inherited
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MinSize {
    public int min() default 0;
    
     public String message() deault "长度太短";
}

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Documented
@Inherited
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DateFormat{
    public String format() default "YYYY-MM-DD";
    
     public String message() deault "时间格式类型有误！";
}

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.text.SimpleDateFormat;
import java.util.HashMap;
import java.util.Map;

public class AnnotationDealUtil {
  public static Map<String, Object> validate(Object bean) {
     Map<String, Object> result = new HashMap<String, Object>();
     result.put("message","验证通过");
     result.put("result", true); 
     Class<?> cls = bean.getClass();
     // 检测field是否存在
    try {
       // 获取实体字段集合
       Field[] fields = cls.getDeclaredFields();
       for(Field f : fields) {
          // 通过反射获取该属性对应的值
          f.setAccessible(true);  
          // 获取字段值
          Object value = f.get(bean);
          Annotation[] arrayAnno = f.getAnnotations();
          for(Annotation annotation : arrayAnno) {
            // 获取注解类型（注解类的Class）
            Class<?> clazz = annotation.annotationType();
            // 获取注解类中的方法集合
            Method[] methodArray = clazz.getDeclaredMethods();
            for (Method method : methodArray) {
                // 获取方法名
                String methodName = method.getName();
                // 过滤错误提示方法的调用
                if(methodName.equals("message")) {
                    continue;
                }
                // 初始化注解验证方法处理类
                Object obj= AnnotationDealUtil.class.newInstance();
                // 获取方法
                try {
                    // 根据方法名获取该方法
                    Method m = obj.getClass().getDeclaredMethod(methodName, Object.class, Field.class);
                    // 调用该fangfa 
                    result = (Map(String, Object>) m.invoke(obj,value, f);
                    // 验证结果 有失败就则退出
                    if(result.get("result").equals(false)) {
                        return result;
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
          }
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return result;
  }
  
  /**
   * 验证是否空值
   *
   */
  public Map<String, Object> isEmpty(Object value, Field field) {
     Map<String, Object> validateResult = new HashMap<String, Object>();
     IsEmptyAnnotation annotation = field.getAnnotation(IsEmptyAnnotation.class);
     if(value == null || value.equals("")) {
        validateResult.put("message", field.getName() + annotation.getMessage());
        validateResult.put("result", false);
     } else {
        validateResult.put("message", "验证通过");
        validateResult.put("result", true);
     }
     return validateResult;
  }
  
  /**
   * 验证最小
   *
   */
  public Map<String, Object> min(Object value, Field field) {
     Map<String, Object> validateResult = new HashMap<String, Object>();
     MinSize annotation = field.getAnnotation(MinSize.class);
     if(value != null && value.toString.length() < annotation.min()){
        validateResult.put("message", annotation.message());
        validateResult.put("result", false);
     } else {
        validateResult.put("message", "验证通过");
        validateResult.put("result", true);
     }
     return validateResult;
  }
  
  /**
   * 验证最大长度
   *
   */
  public Map<String, Object> max(Object value, Field field) {
     Map<String, Object> validateResult = new HashMap<String, Object>();
     MaxSize annotation = field.getAnnotation(MaxSize.class);
     if(value != null && value.toString.length() < annotation.min()){
        validateResult.put("message", annotation.message());
        validateResult.put("result", false);
     } else {
        validateResult.put("message", "验证通过");
        validateResult.put("result", true);
     }
     return validateResult;
  }
  
  /**
   * 验证日期格式
   *
   */
  public Map<String, Object> max(Object value, Field field) {
     Map<String, Object> validateResult = new HashMap<String, Object>();
     DateFormat annotation = field.getAnnotation(DateFormat.class);
     if(value != null && annotation.format() != null){
        validateResult.put("message", "验证通过");
        validateResult.put("result", true);
        SimpleDateFormat dateFormat = new SimpleDateFormat(annotation.format());
        try {
            dateFormat.setLenient(false);
            dateFormat.format(value);
        } catch (Exception e) {
            validateResult.put("message", annotation.message());
            validateResult.put("result", false);
        }
     } else {
        validateResult.put("message", "验证通过");
        validateResult.put("result", true);
     }
     return validateResult;
  }
  
}