自定义注解

参考待整理：https://www.cnblogs.com/yzykkpl/p/10356258.html

获取注解

你需要通过反射来获取运行时注解，可以从 Package、Class、Field、Method...上面获取，基本方法都一样，几个常见的方法如下：

/**
 * 获取指定类型的注解
 */
public <A extends Annotation> A getAnnotation(Class<A> annotationType);
 
/**
 * 获取所有注解，如果有的话
 */
public Annotation[] getAnnotations();
 
/**
 * 获取所有注解，忽略继承的注解
 */
public Annotation[] getDeclaredAnnotations();
 
/**
 * 指定注解是否存在该元素上，如果有则返回true，否则false
 */
public boolean isAnnotationPresent(Class<? extends Annotation> annotationType);
 
/**
 * 获取Method中参数的所有注解
 */
public Annotation[][] getParameterAnnotations();

1.java 自定义注解 （原文：https://blog.csdn.net/github_35180164/article/details/52118286）

注解：

// 适用类、接口（包括注解类型）或枚举
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface ClassInfo {
    String value();
}
// 适用field属性，也包括enum常量
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface FieldInfo {
    int[] value();
}
// 适用方法
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MethodInfo {
    String name() default "long";
    String data();
    int age() default 27;
}

定义一个测试类来使用这些注解：

/**
 * 测试运行时注解
 */
@ClassInfo("Test Class")
public class TestRuntimeAnnotation {
 
    @FieldInfo(value = {1, 2})
    public String fieldInfo = "FiledInfo";
 
    @FieldInfo(value = {10086})
    public int i = 100;
 
    @MethodInfo(name = "BlueBird", data = "Big")
    public static String getMethodInfo() {
        return TestRuntimeAnnotation.class.getSimpleName();
    }
}

获取注解信息：

/**
 * 测试运行时注解
 */
private void _testRuntimeAnnotation() {
    StringBuffer sb = new StringBuffer();
    Class<?> cls = TestRuntimeAnnotation.class;
    Constructor<?>[] constructors = cls.getConstructors();
    // 获取指定类型的注解
    sb.append("Class注解：").append("
");
    ClassInfo classInfo = cls.getAnnotation(ClassInfo.class);
    if (classInfo != null) {
        sb.append(Modifier.toString(cls.getModifiers())).append(" ")
                .append(cls.getSimpleName()).append("
");
        sb.append("注解值: ").append(classInfo.value()).append("

");
    }
 
    sb.append("Field注解：").append("
");
    Field[] fields = cls.getDeclaredFields();
    for (Field field : fields) {
        FieldInfo fieldInfo = field.getAnnotation(FieldInfo.class);
        if (fieldInfo != null) {
            sb.append(Modifier.toString(field.getModifiers())).append(" ")
                    .append(field.getType().getSimpleName()).append(" ")
                    .append(field.getName()).append("
");
            sb.append("注解值: ").append(Arrays.toString(fieldInfo.value())).append("

");
        }
    }
 
    sb.append("Method注解：").append("
");
    Method[] methods = cls.getDeclaredMethods();
    for (Method method : methods) {
        MethodInfo methodInfo = method.getAnnotation(MethodInfo.class);
        if (methodInfo != null) {
            sb.append(Modifier.toString(method.getModifiers())).append(" ")
                    .append(method.getReturnType().getSimpleName()).append(" ")
                    .append(method.getName()).append("
");
            sb.append("注解值: ").append("
");
            sb.append("name: ").append(methodInfo.name()).append("
");
            sb.append("data: ").append(methodInfo.data()).append("
");
            sb.append("age: ").append(methodInfo.age()).append("
");
        }
    }
 
    System.out.print(sb.toString());
}

测试结果：

2.SpringBoot  自定义注解

annotation注解：

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

/**
 * 自定义注解，实现主键自增
 * @author sea
 *
 */
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface AutoIncKey {}

AutoIncKeyEventListener 注解监听器：

package com.sea.test.annotation;

import java.lang.reflect.Field;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.FindAndModifyOptions;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.mapping.event.AbstractMongoEventListener;
import org.springframework.data.mongodb.core.mapping.event.BeforeConvertEvent;
import org.springframework.data.mongodb.core.query.Criteria;
import org.springframework.data.mongodb.core.query.Query;
import org.springframework.data.mongodb.core.query.Update;
import org.springframework.stereotype.Component;
import org.springframework.util.ReflectionUtils;
/**
 * 监听器用于监听MongoEvent
 * ，该类继承AbstractMongoEventListener类，因为我们需要在JAVA对象转换成数据库对象的时候操作id字段实现id自增，
 * 所以覆盖onBeforeConvert方法（详见spring-data文档，https://docs.spring.io/spring-data/data-document/docs/current/reference/html/，5.11节）
 * @author sea
 *
 */
@Component
public class AutoIncKeyEventListener extends AbstractMongoEventListener<Object>{
      private static final Logger logger= LoggerFactory.getLogger(AutoIncKeyEventListener.class);

      @Autowired
      private MongoTemplate mongoTemplate;
      
      
      @Override
      public void onBeforeConvert(BeforeConvertEvent<Object> event) {
          logger.info(event.getSource().toString());
          Object source = event.getSource();
          if (source != null) {
              ReflectionUtils.doWithFields(source.getClass(), new ReflectionUtils.FieldCallback() {
                  public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
                      ReflectionUtils.makeAccessible(field);
                      // 如果字段添加了我们自定义的AutoIncKey注解
                      if (field.isAnnotationPresent(AutoIncKey.class)) 
                      {
                          // 设置自增ID
                          Object value = field.get(source);
                         //获取之前id的值，如果主键不为空，主键加1
                          if(value==null)
                          {
                              field.set(source, getNextId(source.getClass().getSimpleName()));
                          }
                      }
                  }
              });
          }
  
      }
  
      
      private Long getNextId(String collName) {
          Query query = new Query(Criteria.where("collName").is(collName));
          Update update = new Update();
          update.inc("seqId", 1);
          FindAndModifyOptions options = new FindAndModifyOptions();
          options.upsert(true);
          options.returnNew(true);
          SeqInfo seq = mongoTemplate.findAndModify(query, update, options, SeqInfo.class);
          return seq.getSeqId();
      }

      

      
}

序列id  

SeqInfo

import java.io.Serializable;

public class SeqInfo implements Serializable {
    
    private static final long serialVersionUID = 1L;
    private  Long  seqId;

    public Long getSeqId() {
        return seqId;
    }

    public void setSeqId(Long seqId) {
        this.seqId = seqId;
    }

    
}