Java反射时如何获取返回值类型, 如何处理List类型的返回参数

举个例子, 如上图中所示, 两种返回类型一种是List<T>, 一种是对象<T>时, 在写通用代码的时候应该怎么去处理

如果是List

    private Object doSelect(SlsSelect select, SlsTable table, Method method, Object[] args) throws ClassNotFoundException, IllegalAccessException, LogException, InstantiationException {
        String hql = select.value();
        String project = table.project();
        String logStore = table.logStore();
        if(StringUtils.isBlank(hql) || StringUtils.isBlank(project) || StringUtils.isBlank(logStore)) {
            return null;
        }
        ConcurrentHashMap<String, Object> actualParamsMap = getActualParamsMap(method, args);
        String newSQL = questionMark(hql, actualParamsMap);
        System.out.println("newSQL=" + newSQL);

        Class<?> returnType = method.getReturnType();
        boolean asList = Collection.class.isAssignableFrom(returnType);
        if(asList) {
            return doList(method, actualParamsMap, project, logStore, newSQL);
        } else {
            return doOne(method, actualParamsMap, project, logStore, newSQL, returnType);
        }
    }

    private Object doList(Method method, ConcurrentHashMap<String, Object> actualParamsMap, String project, String logStore, String newSQL) throws ClassNotFoundException, LogException, IllegalAccessException, InstantiationException {
        System.out.println("");
        List<Object> list = Collections.synchronizedList(new ArrayList<>());
        ParameterizedType parameterizedType = (ParameterizedType) method.getAnnotatedReturnType();
        Type type = parameterizedType.getActualTypeArguments()[0];
        Class<?> clazz = Class.forName(type.getTypeName());
        Client client = SpringContextUtil.getBean("slsClient");
        List<Map<String, String>> contents = selectList(client, project, logStore, newSQL, (Integer) actualParamsMap.getOrDefault("from", 0), (Integer)actualParamsMap.getOrDefault("to", 0));
        for(Map<String, String> content : contents) {
            Object record = clazz.newInstance();
            Field[] fields = record.getClass().getDeclaredFields();
            for(Field field : fields) {
                String fieldName = field.getName();
                Object fieldValue = content.get(fieldName);
                field.setAccessible(true);
                field.set(record, fieldValue);
            }
            list.add(record);
        }
        return list;
    }

如果是单个对象

    private Object doOne(Method method, ConcurrentHashMap<String, Object> actualParamsMap, String project, String logStore, String newSQL, Class<?> returnType) throws LogException, IllegalAccessException, InstantiationException {
        Field[] declaredFields = returnType.getDeclaredFields();
        Client client = SpringContextUtil.getBean("slsClient");
        List<Map<String, String>> contents = selectList(client, project, logStore, newSQL, (Integer) actualParamsMap.getOrDefault("from", 0), (Integer)actualParamsMap.getOrDefault("to", 0));
        if(contents.size() == 0) {
            return null;
        }
        Map<String, String> content = contents.get(0);
        Object record = returnType.newInstance();
        for(Field field : declaredFields) {
            String fieldName = field.getName();
            Object fieldValue = content.get(fieldName);
            field.setAccessible(true);
            field.set(record, fieldValue);
        }
        return record;
    }

 这是我参考Mybatis的框架写的基于阿里云Sls日志服务写的查询框架, 完整源码太多了没有办法贴, 有需要的化可以评论区留下邮箱.

标签：Java,String,logStore,Object,List,project,newSQL,类型,actualParamsMap
来源： https://blog.csdn.net/qq_29777207/article/details/117397151