摘要：背景微信退款接口需要使用到證書，我參考微信的官方進行，部分代碼如下上面的代碼，在本地調試的時候正常跑過，沒有出現任何異常，但是放到測試環境之后便會出現下面的異常，這三種異常都是從這里拋出來的。

微信退款接口需要使用到證書，我參考微信的官方Demo進行，部分代碼如下：

char[] password = config.getMchID().toCharArray();
InputStream certStream = config.getCertStream();
KeyStore ks = KeyStore.getInstance("PKCS12");
ks.load(certStream, password);

上面的代碼，在本地調試的時候正常跑過，沒有出現任何異常，但是放到測試環境之后便會出現下面的異常，這三種異常都是從ks.load(certStream, password)這里拋出來的。定位這個問題花費了一些時間，且讓我小小總結一下，供大家遇到相同問題時有個參考。

java.io.IOException: Short read of DER length
    at sun.security.util.DerInputStream.getLength(DerInputStream.java:582)
    at sun.security.util.DerValue.init(DerValue.java:391)
    at sun.security.util.DerValue.(DerValue.java:332)
    at sun.security.util.DerValue.(DerValue.java:345)
    at sun.security.pkcs12.PKCS12KeyStore.engineLoad(PKCS12KeyStore.java:1914)
    at java.security.KeyStore.load(KeyStore.java:1445)
    at com.lingyejun.authenticator.ReadPKCS12File$LoadCertInputStream.run(ReadPKCS12File.java:53)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

java.io.IOException: DerInputStream.getLength(): lengthTag=7, too big.
    at sun.security.util.DerInputStream.getLength(DerInputStream.java:599)
    at sun.security.util.DerValue.init(DerValue.java:391)
    at sun.security.util.DerValue.(DerValue.java:332)
    at sun.security.util.DerValue.(DerValue.java:345)
    at sun.security.pkcs12.PKCS12KeyStore.engineLoad(PKCS12KeyStore.java:1914)
    at java.security.KeyStore.load(KeyStore.java:1445)
    at com.lingyejun.authenticator.ReadPKCS12File$LoadCertInputStream.run(ReadPKCS12File.java:53)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

java.io.IOException: toDerInputStream rejects tag type 54
    at sun.security.util.DerValue.toDerInputStream(DerValue.java:874)
    at sun.security.pkcs12.PKCS12KeyStore.engineLoad(PKCS12KeyStore.java:1915)
    at java.security.KeyStore.load(KeyStore.java:1445)
    at com.lingyejun.authenticator.ReadPKCS12File$LoadCertInputStream.run(ReadPKCS12File.java:53)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)

結論：keyStore.load(InputStream stream, char[] password)中的InputStream在嘗試加載的過程中，如果有其他的線程正在使用或者進行同樣的讀加載，那么就會拋出上面的異常。

package com.lingyejun.authenticator;
 
import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import java.io.IOException;
import java.io.InputStream;
import java.security.*;
import java.security.cert.CertificateException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
 
/**
 * 模擬加載certStream問題
 *
 * @Author: lingyejun
 * @Date: 2019/6/24
 * @Describe:
 * @Modified By:
 */
public class ReadPKCS12File {
 
    // 線程個數
    private static final int THREAD_POOL_SIZE = 10;
 
    // 初始化線程池
    private ExecutorService executorService = new ThreadPoolExecutor(THREAD_POOL_SIZE, THREAD_POOL_SIZE,
            0L, TimeUnit.MILLISECONDS,
            new LinkedBlockingQueue());
 
    // HTTPS證書的本地路徑
    private static final String CERT_LOCAL_PATH = "apiclient_cert.p12";
 
    // HTTPS證書密碼，默認密碼等于商戶號MCHID
    private static final String CERT_PASSWORD = "1509107311";
 
    private static InputStream certStream = ReadPKCS12File.class.getClassLoader().getResourceAsStream(CERT_LOCAL_PATH);
 
 
    public static void main(String[] args) {
 
        ReadPKCS12File readPKCS12File = new ReadPKCS12File();
        for (int threadNo = 0; threadNo < THREAD_POOL_SIZE; threadNo++) {
            readPKCS12File.executorService.execute(readPKCS12File.new LoadCertInputStream());
        }
        readPKCS12File.executorService.shutdown();
    }
 
    public class LoadCertInputStream implements Runnable {
 
        @Override
        public void run() {
            // 證書
            char[] password = CERT_PASSWORD.toCharArray();
            InputStream certStream = ReadPKCS12File.certStream;
            try {
                KeyStore ks = KeyStore.getInstance("PKCS12");
                ks.load(certStream, password);
 
                // 實例化密鑰庫 & 初始化密鑰工廠
                KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
                kmf.init(ks, password);
 
                // 創建 SSLContext
                SSLContext sslContext = SSLContext.getInstance("TLS");
                sslContext.init(kmf.getKeyManagers(), null, new SecureRandom());
 
                // 余下代碼就不寫了，，，
 
                System.out.println("初始化SSL成功！");
 
            } catch (IOException e) {
                e.printStackTrace();
            } catch (CertificateException e) {
                e.printStackTrace();
            } catch (NoSuchAlgorithmException e) {
                e.printStackTrace();
            } catch (UnrecoverableKeyException e) {
                e.printStackTrace();
            } catch (KeyStoreException e) {
                e.printStackTrace();
            } catch (KeyManagementException e) {
                e.printStackTrace();
            }
        }
    }
}

知道問題之后，我們只需要將certStream由全局唯一更改為方法的局部變量即可

InputStream certStream = ReadPKCS12File.certStream

改為

InputStream certStream = ReadPKCS12File.class.getClassLoader().getResourceAsStream(CERT_LOCAL_PATH)

微信的官方Demo中的，InputStream certStream = config.getCertStream()，這行代碼把我給"誤導"了，我是在外部讀取的pkcs12文件輸入流且config對象是單例的，導致多個線程共同訪問這行代碼時，certStream不能被正常加載，故出現了上面的問題。