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Random java.util.Random 其實一點也不 Random, 因為屬於一種線性分佈, 線性不比離散, 所以就是有公式可以預測啦~ 大神的論文在 這裡 https://stackoverflow.com/questions/11051205/difference-between-java-util-random-and-java-security-securerandom The standard Oracle JDK 7 implementation uses what's called a Linear Congruential Generator to produce random values in java.util.Random. Predictability of Linear Congruential Generators Hugo Krawczyk wrote a pretty good paper about how these LCGs can be predicted ("How to predict congruential generators"). If you're lucky and interested, you may still find a free, downloadable version of it on the web. And there's plenty more research that clearly shows that you should never use an LCG for security-critical purposes. This also means that your random numbers are predictable right now, something you don't want for session IDs and the like. 隨機數安全議題 http://wps2015.org/drops/drops/%E8%81%8A%E4%B8%80%E8%81%8A%E9%9A%8F%E6%9C%BA%E6%95%B0%E5%AE%89%E5%85%A8.html Secu...

Chung Nguyen Sample Data [ {"uid":"1","name":"阿花","age":38,"gender":"F"}, {"uid":"2","name":"阿瓜","age":28,"gender":"M"} ] Entity @Data @JsonInclude(JsonInclude.Include.NON_NULL) @JsonPropertyOrder(value = { "uid", "name", "age", "gender" }) public class Customer { // creativeId equals adId @JsonProperty("uid") private String uid; @JsonProperty("name") private String name; @JsonProperty("age") private Integer age; @JsonProperty("gender") private String gender; } Test @Test public void test() throws IOException { List<Customer> customerList = objectMapper.readValue(json, new TypeReference >() {}); Map customerMap = customerList.stream() .collect(Collectors.toMap( ...

Optional Java 最大的敵人, 我想應該就是 NPT Exception , tears. 所以 Java8 設計了一個 Optional 用來解決 NPT 這淘氣的小東西, fuck. 詳細的使用方式 參閱這個 bloger 的介紹, 寫的超棒, 我覺得啦 :) JpaRepository Spring framework 做 CRUD 的好朋友, 就是 JpaRepository , 沒有用 Optional 的寫法像這樣 @Repository public interface UserInfoRepository extends JpaRepository<UserInfo, String> { UserInfo findByName(String name); } 這樣寫其實也沒什麼不合理, 只是在商業邏輯處理時, 要多一個 if 判斷, 判斷是否有查詢到 userInfo 的資料. public void business() { UserInfo user = userInfoRepository.findByName("dumdum"); if (Objects.isNull(user)) { // throw exception } else { // do something } } 改為用 Optional 試試看 @Repository public interface UserInfoRepository extends JpaRepository<UserInfo, String> { Optional<Userinfo> findByName(String name); } public void business() { Optional<Userinfo> userOpt = userInfoRepository.findByName("dumdum"); UserInfo user = userOpt.orElseThrow(() -> new Exception(...

1. 產生 SSL certificate keytool -genkey -alias tomcat -storetype PKCS12 -keyalg RSA -keysize 2048 -keystore keystore.p12 -validity 3650 Enter keystore password: Re-enter new password: What is your first and last name? [Unknown]: jerry What is the name of your organizational unit? [Unknown]: td What is the name of your organization? [Unknown]: com What is the name of your City or Locality? [Unknown]: taipei What is the name of your State or Province? [Unknown]: taiwan What is the two-letter country code for this unit? [Unknown]: tw Is CN=jarvis, OU=td, O=urad, L=taipei, ST=taiwan, C=tw correct? [no]: yes 這個 certificate 是 self-signed certificate 沒有經過第三方認證, 所以沒有公信力, 正式上線會在瀏覽器看到 連線不被信任 要有公信力的 certificate 最簡單的是 Lets Encrypt , 其他就是花一些錢找簽發 certificate 的組織 2. Enable HTTPS in Spring Boot Spring Boot 內建的 tomcat 預設 http 是 8080, Spring Boot 可以設定 http 跟 https, 但沒辦法同時存在這兩個設定, 如果要同時存在兩種 connection, 建議依照 文件 建議設定 https, 再透過 programmatically 去設定 http 會比較容易。 相關範例可以參考 : https://...

Entity @Data @NoArgsConstructor @AllArgsConstructor @Entity(name = "messenger") @IdClass(MessengerPrimaryKey.class) public class Messenger implements Serializable { @Id @Column(name = "user_id", length = 64, nullable = false) private String userId; @Id @Column(name = "psid", length = 64, nullable = false) private String psId; @Column(name = "page_id", length = 64, nullable = false) private String pageId; } PrimaryKey @Data @NoArgsConstructor @AllArgsConstructor public class MessengerPrimaryKey implements Serializable { private String userId; private String psId; } Test1 transactionalTest1 是基本的 transactional, 在 transactionalTest1 結束後會做一個 commit import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.boot.test.context.SpringBootTest; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.transaction.annotation.Transactional; import tw.com.u...

Todd Quackenbush Facebook Messenger Platform 最主要的還是看文件, 偶而需要使用 Facebook Search 功能, 可以看到神秘版的文件。 1. 粉絲頁 與 App 的關係 在開發 Bot 之前, 需要做幾件事情 申請 facebook app 申請 facebook fans-page 規劃流程, 最好有一個懂 UX 的開發者 參與, 不然流程會很 XD 一個 bot 需要一個處理各種 events 的 callback, 一個 app 只能設定一個 callback, 所以 bot 跟 app 是 1 對 1 的關係, 一個 page 可以被最多 10 個 app 訂閱, 所以 page 跟 app 是 1 對 n(n 的關係, 這會有什麼影響呢？ 在多人協作開發的時候, 你的好 partner 會送很多 event 給你, 禮尚往來, 你也會送一些 event 給他, 有幾個方式 從原生 App 申請一組開發 app 出來, webhook 只設定自己開發要用的 event 額外申請一個自己專用的 Fans-Page, 來 subscribed 2. GetStartButton Not Work 這邊的雷是因為, 自己開發的時候只 hook 了 messages 這個 event, 後來開發的時候, 就乾脆都拿, 之後再看用了哪些功能在慢慢推給 Facebook 審核 check GetStartButton setting curl -X GET "https://graph.facebook.com/v2.10/me/messenger_profile?fields=get_started&access_token= " check webhook messaging_postbacks event check your callback rsources is exist.