背景

微信退款接口需要使用到证书，我参考微信的官方 Demo 进行，部分代码如下：

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

上面的代码，在本地调试的时候正常跑过，没有出现任何异常，但是放到测试环境之后便会出现下面的异常，这三种异常都是从 ks.load(certStream, password) 这里抛出来的。定位这个问题花费了一些时间，且让我小小总结一下，供大家遇到相同问题时有个参考。

异常类型 1

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.<init>(DerValue.java:332)
    at sun.security.util.DerValue.<init>(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)

异常类型 2

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.<init>(DerValue.java:332)
    at sun.security.util.DerValue.<init>(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)

异常类型 3

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)

结论：keyStore.load(InputStream stream, char[] password) 中的 InputStream 在尝试加载的过程中，如果有其他的线程正在使用或者进行同样的读加载，那么就会抛出上面的异常。

模拟复现

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;
 
/**
 * 模拟加载 certStream 问题
 *
 * @Author: lingyejun
 * @Date: 2019/6/24
 * @Describe:
 * @Modified By:
 */
public class ReadPKCS12File {
 
    // 线程个数
    private static final int THREAD_POOL_SIZE = 10;
 
    // 初始化线程池
    private ExecutorService executorService = new ThreadPoolExecutor(THREAD_POOL_SIZE, THREAD_POOL_SIZE,
            0L, TimeUnit.MILLISECONDS,
            new LinkedBlockingQueue<Runnable>());
 
    // HTTPS 证书的本地路径
    private static final String CERT_LOCAL_PATH = "apiclient_cert.p12";
 
    // HTTPS 证书密码，默认密码等于商户号 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() {
            // 证书
            char[] password = CERT_PASSWORD.toCharArray();
            InputStream certStream = ReadPKCS12File.certStream;
            try {KeyStore ks = KeyStore.getInstance("PKCS12");
                ks.load(certStream, password);
 
                // 实例化密钥库 & 初始化密钥工厂
                KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
                kmf.init(ks, password);
 
                // 创建 SSLContext
                SSLContext sslContext = SSLContext.getInstance("TLS");
                sslContext.init(kmf.getKeyManagers(), null, new SecureRandom());
 
                // 余下代码就不写了，，，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();
            }
        }
    }
}

知道问题之后，我们只需要将 certStream 由全局唯一更改为方法的局部变量即可

InputStream certStream = ReadPKCS12File.certStream

改为

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

究其原因

微信的官方 Demo 中的，InputStream certStream = config.getCertStream()，这行代码把我给 ’ 误导 ’ 了，我是在外部读取的 pkcs12 文件输入流且 config 对象是单例的，导致多个线程共同访问这行代码时，certStream 不能被正常加载，故出现了上面的问题。