九、开发中常用的工具类方法总结

public static String formatDate(Date dateTime, String pattern) {
    if (dateTime != null && !StringUtils.isEmpty(pattern)) {
        DateFormat df = new SimpleDateFormat(pattern);
        String result = df.format(dateTime);
        return result;
    } else {
        return "";
    }
}

备注：pattern可能的取值
public static final String FORMAT_LONG0 = "yyyyMMddHHmmss";
public static final String FORMAT_LONG = "yyyy-MM-dd HH:mm:ss";
public static final String FORMAT_LONG2 = "yyyy/MM/dd HH:mm:ss";
public static final String FORMAT_LONG3 = "yyyy.MM.dd HH:mm:ss";
public static final String FORMAT_LONG4 = "yyyy-MM-dd";
public static final String FORMAT_LONG5 = "yyyyMMddHHmmssSSS";

3.1字符串判断是否为空
public static boolean isEmpty(String str) {
        return str == null || str.length() == 0;
}

3.2集合判断是否为空： commons-collections.jar下面
org.apache.commons.collections.CollectionUtils#isEmpty
public static boolean isEmpty(Collection coll) {
        return coll == null || coll.isEmpty();
}

3.2集合map是否为空： commons-collections.jar下面
public static boolean isEmpty(Map map) {
    return map == null || map.isEmpty();
}

public static void main(String[] args) {
        UserDto userDto=new UserDto();
        //javaBean转化为dto
        Map<String, Object> stringObjectMap1 = toMap(userDto);
        System.out.println(stringObjectMap1);
        Map<String, Object> stringObjectMap = new HashMap<>();
        stringObjectMap.put("address","ccc");
        stringObjectMap.put("userName","zjb");
        stringObjectMap.put("code","11");
        try {
            //map 转化为javaBean
            convertMap(userDto.getClass(),stringObjectMap);
        } catch (IntrospectionException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }

    /**
     * 将一个 JavaBean 对象转化为一个 Map
     * @param bean 要转化的JavaBean 对象
     * @return 转化出来的 Map 对象
     * @throws IntrospectionException 如果分析类属性失败
     * @throws IllegalAccessException 如果实例化 JavaBean 失败
     * @throws InvocationTargetException 如果调用属性的 setter 方法失败
     */
    @SuppressWarnings("rawtypes")
    public static Map<String,Object> toMap(Object bean) {
        Class<? extends Object> clazz = bean.getClass();
        Map<String, Object> returnMap = new HashMap<String, Object>();
        BeanInfo beanInfo = null;
        try {
            beanInfo = Introspector.getBeanInfo(clazz);
            PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
            for (int i = 0; i < propertyDescriptors.length; i++) {
                PropertyDescriptor descriptor = propertyDescriptors[i];
                String propertyName = descriptor.getName();
                if (StringUtils.isNotEmpty(propertyName)&&!"class".equals(propertyName)) {
                    Method readMethod = descriptor.getReadMethod();
                    Object result = null;
                    result = readMethod.invoke(bean, new Object[0]);
                    propertyName = propertyName.toString();
                    if (null != result) {
                        result = result.toString();
                    }
                    returnMap.put(propertyName, result);
                }
            }
        } catch (Exception e) {
            //异常日志信息捕获并打印

        }
        return returnMap;
    }

    /**
     * 将一个 Map 对象转化为一个 JavaBean
     * @param type 要转化的类型
     * @param map 包含属性值的 map
     * @return 转化出来的 JavaBean 对象
     * @throws IntrospectionException
     *             如果分析类属性失败
     * @throws IllegalAccessException
     *             如果实例化 JavaBean 失败
     * @throws InstantiationException
     *             如果实例化 JavaBean 失败
     * @throws InvocationTargetException
     *             如果调用属性的 setter 方法失败
     */
    public static Object convertMap(Class type, Map map)
            throws IntrospectionException, IllegalAccessException,
            InstantiationException, InvocationTargetException {
        BeanInfo beanInfo = Introspector.getBeanInfo(type); // 获取类属性
        Object obj = type.newInstance(); // 创建 JavaBean 对象
        System.out.println(obj.toString());
        try{
            // 给 JavaBean 对象的属性赋值
            PropertyDescriptor[] propertyDescriptors =  beanInfo.getPropertyDescriptors();
            for (int i = 0; i< propertyDescriptors.length; i++) {
                PropertyDescriptor descriptor = propertyDescriptors[i];
                String propertyName = descriptor.getName();
                if (map.containsKey(propertyName)) {
                    // 下面一句可以 try 起来，这样当一个属性赋值失败的时候就不会影响其他属性赋值。
                    Object value = map.get(propertyName);

                    Object[] args = new Object[1];
                    args[0] = value;

                    descriptor.getWriteMethod().invoke(obj, args);
                }
            }
            System.out.println(obj.toString());
        }catch (Exception e){
            //异常日志信息捕获并打印

        }
        return obj;
    }