@Trim注解，修建字符串开头和结尾的空白

偏执的太偏执、 2023-02-09 13:26 10阅读 0赞

1.  注解

@Target({ElementType.FIELD, ElementType.PARAMETER})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface Trim {
    }

1.  注解解析器

@Slf4j
    public class TrimResolver implements FieldResolver {
    
        /**
         * 遍历传入对象的属性（Field），
         * <p>
         * 如果持有 {@link Trim @Trim} 注解，修剪字符串开头和结尾的空白。
         * <p>
         * 如果持有 {@link Trim @Trim} 注解的属性的值不是String类型，则递归遍历该属性引用的对象。
         *
         * @param obj
         * @see String#trim()
         */
        public void trim(Object obj) {
            try {
                this.resolve(obj);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    
        @Override
        public void doResolve(Object obj) throws Exception {
            this.resolveFields(obj);
        }
    
        @Override
        public void resolveField(Object obj, Field field) throws InvocationTargetException, IllegalAccessException {
            Class<?> clazz = obj.getClass();
            Trim trimAnnotation = field.getAnnotation(Trim.class);
            if (trimAnnotation == null) {
                return;
            }
            // 获取持有 @Trim 注解的字段的值
            Object fieldValue = BeanUtil.readField(obj, field,
                    () -> log.warn("持有@Trim注解的字段[{}#{}]缺少Getter方法", clazz.getName(), field.getName()));
            // 如果持有 @Trim 注解的字段的值不是 String 类型，则递归遍历该字段引用的对象。
            if (!(fieldValue instanceof String)) {
                this.trim(fieldValue);
                return;
            }
            // 修剪字符串开头和结尾的空白
            String trimValue = this.trim((String) fieldValue);
            // 给持有 @Trim 注解的字段赋值
            BeanUtil.writeField(obj, field, trimValue,
                    () -> log.warn("持有@Trim注解的字段[{}#{}]缺少Setter方法", clazz.getName(), field.getName()));
        }
    
        @Override
        @SuppressWarnings("unchecked")
        public void resolveCollection(Collection collection) throws Exception {
            Object[] array = collection.toArray();
            this.resolveArray(array);
            collection.clear();
            collection.addAll(Arrays.asList(array));
        }
    
        @Override
        public void resolveArray(Object array) throws Exception {
            int length = Array.getLength(array);
            for (int i = 0; i < length; i++) {
                Object item = Array.get(array, i);
                if (item instanceof String) {
                    Array.set(array, i, this.trim((String) item));
                    continue;
                }
                this.resolve(item);
            }
        }
    
        private String trim(String s) {
            if (s == null) {
                return null;
            }
            return s.trim();
        }
    
    }

1.  用法  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyMTM2MjUw_size_16_color_FFFFFF_t_70]  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyMTM2MjUw_size_16_color_FFFFFF_t_70 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyMTM2MjUw_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200519091238969.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyMTM2MjUw,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyMTM2MjUw_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200519091247766.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyMTM2MjUw,size_16,color_FFFFFF,t_70