2017年12月4日星期一

計算佔用記憶體


    private static final long MEGABYTE = 1024L * 1024L;

    public static long bytesToMegabytes(long bytes) {
        return bytes / MEGABYTE;
    }

    public static void main(String[] args) throws Exception {
        runGC();

        long start = usedMemory();

        // Do Something ...

        long used = usedMemory() - start;
        System.out.println("Used memory is bytes: " + used);
        System.out.println("Used memory is megabytes: " + bytesToMegabytes(used));
    }

    private static final Runtime s_runtime = Runtime.getRuntime();

    private static long usedMemory() {
        return s_runtime.totalMemory() - s_runtime.freeMemory();
    }

    private static void runGC() throws Exception {
        long usedMem1 = usedMemory(), usedMem2 = Long.MAX_VALUE;
        for (int i = 0; (usedMem1 < usedMem2) && (i < 500); ++i) {
            s_runtime.runFinalization();
            s_runtime.gc();
            Thread.currentThread().yield();
            usedMem2 = usedMem1;
            usedMem1 = usedMemory();
        }
    }

2017年9月27日星期三

Jackson @JsonFormat.lenient Date validate

前幾天遇到了Jackson convert String to Date 的問題，因為字串轉日期預設是寬容的 ( lenient = true )，所以會在盡量不出錯 ( ParseException ) 的狀況下容錯，但這樣卻會造成資料內容錯誤，例如：輸入字串 "2017-02-29"，會輸出 Wed Mar 01 00:00:00 CST 2017

先介紹一下專案環境

Jersey2. RESTful Web Service.
Swagger. Autogenerate Document.
Gradle. Build, Test, Dependent management

build.gralde

compile group: 'org.glassfish.jersey.containers', name: 'jersey-container-servlet-core', version: '2.25.1'
compile group: 'org.glassfish.jersey.ext', name: 'jersey-spring3', version: '2.25.1'
compile group: 'org.glassfish.jersey.media', name: 'jersey-media-json-jackson', version: '2.25.1'
compile group: 'io.swagger', name: 'swagger-core', version: '1.5.13'
compile group: 'io.swagger', name: 'swagger-jersey2-jaxrs', version: '1.5.13'

Solution

@JsonFormat(lenient = false)

可以參考這裡，簡單來說，這個問題在 2016/11/4 就已經有人提 Issue 出來，並在同年 11/16 就已加入 2.9 版；只要將 jackson-annotations:2.8.5 升級至 2.9.0，@JsonFormat annotation 即可設定 lenient attribute。

但這裡遇到個問題，可以參考這裡，升版後，會出現以下錯誤；因為 Swagger-core 1.5.13 depends on Jackson 2.8.5. 但 2.9.0 的某個 Method 被拿掉了。（這個問題後來在 Jackson 2.9.1 修復了）

java.lang.NoSuchMethodError: com.fasterxml.jackson.databind.introspect.AnnotatedMember.annotations()Ljava/lang/Iterable;

@JsonDeserialize(using = DateDeserializer.class)

後來考慮到 Jackson 2.9.x 穩定性問題，怕又會有什麼奇怪的錯誤，所以在不升版的情況下，繼承 JsonDeserializer 實作 Date 型態的反序列化，範例如下：

public class DateDeserializer extends JsonDeserializer {

    @Override
    public Date deserialize(JsonParser parser, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        sdf.setLenient(false);
        String text = parser.getText();
        try {
            Date date = sdf.parse(text);
            return date;
        } catch (ParseException e) {
            throw new RuntimeException("Date Parse 錯誤! 請檢查格式與合法性");
        }
    }

}

2017年9月26日星期二

Live Document

Swagger V.S. apidoc

http://swagger.io/

Swagger Core - Java-related libraries for generating and reading Swagger definitions

Swagger UI to generate interactive web-based documentation

Swagger Codegen - Command-line tool for generating both client and server side code from a Swagger definition

Swagger Editor - Browser based editor for authoring Swagger definitions in YAML or JSON format

https://github.com/swagger-api/swagger-core/wiki/Annotations-1.5.X

apiDoc creates a documentation from API annotations in your source code.

評估考量

文件與程式邏輯同步性
統一格式 (易用性、可讀性)
學習成本 (門檻)
版本修改紀錄

Swagger

優：

定義明確的 OpenAPI Specification
工具多 (基於 OpenAPI Specification)
網路資源多
同步性高

缺：

學習成本高，入門不易
必須是 Web Project
Project 必須引入 Swagger Library

apiDoc

Install
```
npm install apidoc -g
```

Use
```
apidoc -i /example -o /apidoc
```

優：

類似 Javadoc 寫法
no need to inject third party library
have version change log
easy to convert apidoc to swagger [https://github.com/fsbahman/apidoc-swagger]

缺：

註解行數多於程式碼
註解終歸是註解，還是有與程式邏輯不同步的可能性

2017年8月30日星期三

Redirect http into https using load balancer

https://forums.aws.amazon.com/thread.jspa?messageID=745509

The Apache block above caused our ELB health check to fail from the HTTP 301 response. To allow this and other local requests over HTTP while redirecting external requests through the ELB to HTTPS, adjust the rewrite condition to match on http instead of a negative match on https:

RewriteEngine on
RewriteCond %{HTTP:X-Forwarded-Proto} ^http$
RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]

2017年8月29日星期二

PKIX：unable to find valid certification path to requested target

/* 
 * Copyright 2006 Sun Microsystems, Inc.  All Rights Reserved. 
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions 
 * are met: 
 * 
 *   - Redistributions of source code must retain the above copyright 
 *     notice, this list of conditions and the following disclaimer. 
 * 
 *   - Redistributions in binary form must reproduce the above copyright 
 *     notice, this list of conditions and the following disclaimer in the 
 *     documentation and/or other materials provided with the distribution. 
 * 
 *   - Neither the name of Sun Microsystems nor the names of its 
 *     contributors may be used to endorse or promote products derived 
 *     from this software without specific prior written permission. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR 
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.security.KeyStore;
import java.security.MessageDigest;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLException;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;

public class InstallCert {

    public static void main(String[] args) throws Exception {
        String host;
        int port;
        char[] passphrase;
        if ((args.length == 1) || (args.length == 2)) {
            String[] c = args[0].split(":");
            host = c[0];
            port = (c.length == 1) ? 443 : Integer.parseInt(c[1]);
            String p = (args.length == 1) ? "changeit" : args[1];
            passphrase = p.toCharArray();
        } else {
            System.out.println("Usage: java InstallCert [:port] [passphrase]");
            return;
        }

        File file = new File("jssecacerts");
        if (file.isFile() == false) {
            char SEP = File.separatorChar;
            File dir = new File(System.getProperty("java.home") + SEP + "lib" + SEP + "security");
            file = new File(dir, "jssecacerts");
            if (file.isFile() == false) {
                file = new File(dir, "cacerts");
            }
        }
        System.out.println("Loading KeyStore " + file + "...");
        InputStream in = new FileInputStream(file);
        KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
        ks.load(in, passphrase);
        in.close();

        SSLContext context = SSLContext.getInstance("TLS");
        TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
        tmf.init(ks);
        X509TrustManager defaultTrustManager = (X509TrustManager) tmf.getTrustManagers()[0];
        SavingTrustManager tm = new SavingTrustManager(defaultTrustManager);
        context.init(null, new TrustManager[] { tm }, null);
        SSLSocketFactory factory = context.getSocketFactory();

        System.out.println("Opening connection to " + host + ":" + port + "...");
        SSLSocket socket = (SSLSocket) factory.createSocket(host, port);
        socket.setSoTimeout(10000);
        try {
            System.out.println("Starting SSL handshake...");
            socket.startHandshake();
            socket.close();
            System.out.println();
            System.out.println("No errors, certificate is already trusted");
        } catch (SSLException e) {
            System.out.println();
            e.printStackTrace(System.out);
        }

        X509Certificate[] chain = tm.chain;
        if (chain == null) {
            System.out.println("Could not obtain server certificate chain");
            return;
        }

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        System.out.println();
        System.out.println("Server sent " + chain.length + " certificate(s):");
        System.out.println();
        MessageDigest sha1 = MessageDigest.getInstance("SHA1");
        MessageDigest md5 = MessageDigest.getInstance("MD5");
        for (int i = 0; i < chain.length; i++) {
            X509Certificate cert = chain[i];
            System.out.println(" " + (i + 1) + " Subject " + cert.getSubjectDN());
            System.out.println("   Issuer  " + cert.getIssuerDN());
            sha1.update(cert.getEncoded());
            System.out.println("   sha1    " + toHexString(sha1.digest()));
            md5.update(cert.getEncoded());
            System.out.println("   md5     " + toHexString(md5.digest()));
            System.out.println();
        }

        System.out.println("Enter certificate to add to trusted keystore or 'q' to quit: [1]");
        String line = reader.readLine().trim();
        int k;
        try {
            k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1;
        } catch (NumberFormatException e) {
            System.out.println("KeyStore not changed");
            return;
        }

        X509Certificate cert = chain[k];
        String alias = host + "-" + (k + 1);
        ks.setCertificateEntry(alias, cert);

        OutputStream out = new FileOutputStream("jssecacerts");
        ks.store(out, passphrase);
        out.close();

        System.out.println();
        System.out.println(cert);
        System.out.println();
        System.out.println("Added certificate to keystore 'jssecacerts' using alias '" + alias + "'");
    }

    private static final char[] HEXDIGITS = "0123456789abcdef".toCharArray();

    private static String toHexString(byte[] bytes) {
        StringBuilder sb = new StringBuilder(bytes.length * 3);
        for (int b : bytes) {
            b &= 0xff;
            sb.append(HEXDIGITS[b >> 4]);
            sb.append(HEXDIGITS[b & 15]);
            sb.append(' ');
        }
        return sb.toString();
    }

    private static class SavingTrustManager implements X509TrustManager {

        private final X509TrustManager tm;
        private X509Certificate[] chain;

        SavingTrustManager(X509TrustManager tm) {
            this.tm = tm;
        }

        public X509Certificate[] getAcceptedIssuers() {
            throw new UnsupportedOperationException();
        }

        public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            throw new UnsupportedOperationException();
        }

        public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            this.chain = chain;
            tm.checkServerTrusted(chain, authType);
        }
    }

}

解决PKIX：unable to find valid certification path to requested target 的问题

訂閱：文章 (Atom)

好好吃飯，好好睡覺，認真做每件事

2017年12月4日星期一

計算佔用記憶體

2017年9月27日星期三

Jackson @JsonFormat.lenient Date validate

先介紹一下專案環境

build.gralde

Solution

@JsonFormat(lenient = false)

@JsonDeserialize(using = DateDeserializer.class)

2017年9月26日星期二

Swagger v.s. apiDoc

Live Document

2017年8月30日星期三

Redirect http into https using load balancer

2017年8月29日星期二

PKIX：unable to find valid certification path to requested target

2017年12月4日 星期一

計算佔用記憶體

2017年9月27日 星期三

Jackson @JsonFormat.lenient Date validate

先介紹一下專案環境

build.gralde

Solution

@JsonFormat(lenient = false)

@JsonDeserialize(using = DateDeserializer.class)

2017年9月26日 星期二

Swagger v.s. apiDoc

Live Document

2017年8月30日 星期三

Redirect http into https using load balancer

2017年8月29日 星期二

PKIX：unable to find valid certification path to requested target

2017年12月4日星期一

2017年9月27日星期三

2017年9月26日星期二

2017年8月30日星期三

2017年8月29日星期二