JavaMail中出错：PKIX路径生成失败无法找到请求目标的有效证书路径

我正在尝试在android中构建一个电子邮件客户端应用程序，现在我想配置javaMail部分

我正在尝试与imap服务器建立连接，但我的代码有问题。。 这是我的密码：

package mailpackage;

import java.util.Properties;

import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.NoSuchProviderException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Store;

public class Connection implements Runnable
{
    boolean done;

    public Connection()
    {
        this.done=false;
    }

    @Override
    public void run()
    {
        System.out.println("Hello from Connection Thread!");
        while(!done)
        {
            String host = "myhost";// change accordingly
            String mailStoreType = "imap";
            String username = "myusername";// change accordingly
            String password = "mypasswd";// change accordingly

            check(host, mailStoreType, username, password);

        }
    }

    public static void receiveEmail(String host, String storeType,  String username, String password)
{
    try
    {
        Properties properties = new Properties();  
        properties.put("mail.imap.com", host);  
        properties.put("mail.imap.starttls.enable","true");
        properties.put("mail.imap.auth", "true");  // If you need to authenticate

        // Use the following if you need SSL
        properties.put("mail.imap.socketFactory.port", 993);
        properties.put("mail.imap.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
        properties.put("mail.imap.socketFactory.fallback", "false");

        Session emailSession = Session.getDefaultInstance(properties);  
        emailSession.setDebug(true);

        //2) create the IMAP store object and connect with the Imap server  
        IMAPStore emailStore = (IMAPStore) emailSession.getStore(storeType);

        emailStore.connect(host, username, password);  

        //3) create the folder object and open it  
        Folder emailFolder = emailStore.getFolder("INBOX");  
        emailFolder.open(Folder.READ_ONLY);  

        //4) retrieve the messages from the folder in an array and print it  
        Message[] messages = emailFolder.getMessages();  
        for (int i = 0; i <messages.length; i++) 
        {
            Message message = messages[i];  
            MimeMessage m = new MimeMessage(emailSession);
            m.setContent(((MimeMessage)messages[i]).getContent() , "text/plain; charset=UTF-8");
            System.out.println("---------------------------------");  
            System.out.println("Email Number " + (i + 1));  
            System.out.println("Subject: " + message.getSubject());  
            System.out.println("From: " + message.getFrom()[0]);  
            System.out.println("Text: " + message.getContent().toString());  
            m.writeTo(System.out);
        }  

        //5) close the store and folder objects  
        emailFolder.close(false);  
        emailStore.close();  

    } 
    catch (NoSuchProviderException e) {e.printStackTrace();}   
    catch (MessagingException e) {e.printStackTrace();}  
    catch (IOException e) {e.printStackTrace();}

}

    public void stopThread()
    {
        this.done=true;
    }
}

我得到以下错误：

javax.mail.MessagingException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target;
  nested exception is:
    javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:571)
    at javax.mail.Service.connect(Service.java:288)
    at javax.mail.Service.connect(Service.java:169)
    at mailpackage.Connection.check(Connection.java:63)
    at mailpackage.Connection.run(Connection.java:33)
    at java.lang.Thread.run(Thread.java:744)
Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
    at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1884)
    at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:276)
    at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:270)
    at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1341)
    at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:153)
    at sun.security.ssl.Handshaker.processLoop(Handshaker.java:868)
    at sun.security.ssl.Handshaker.process_record(Handshaker.java:804)
    at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1016)
    at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1312)
    at sun.security.ssl.SSLSocketImpl.readDataRecord(SSLSocketImpl.java:882)
    at sun.security.ssl.AppInputStream.read(AppInputStream.java:102)
    at com.sun.mail.util.TraceInputStream.read(TraceInputStream.java:110)
    at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
    at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
    at com.sun.mail.iap.ResponseInputStream.readResponse(ResponseInputStream.java:98)
    at com.sun.mail.iap.Response.<init>(Response.java:96)
    at com.sun.mail.imap.protocol.IMAPResponse.<init>(IMAPResponse.java:61)
    at com.sun.mail.imap.protocol.IMAPResponse.readResponse(IMAPResponse.java:135)
    at com.sun.mail.imap.protocol.IMAPProtocol.readResponse(IMAPProtocol.java:261)
    at com.sun.mail.iap.Protocol.<init>(Protocol.java:114)
    at com.sun.mail.imap.protocol.IMAPProtocol.<init>(IMAPProtocol.java:104)
    at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:538)
    ... 5 more
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:385)
    at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:292)
    at sun.security.validator.Validator.validate(Validator.java:260)
    at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:326)
    at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:231)
    at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:126)
    at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1323)
    ... 23 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:196)
    at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:268)
    at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:380)
    ... 29 more

javax.mail.MessaginException:sun.security.validator.ValidatorException:PKIX路径生成失败：sun.security.provider.certpath.SunCertPathBuilderException:找不到请求目标的有效证书路径；
嵌套异常是：
javax.net.ssl.SSLHandshakeException:sun.security.validator.ValidatorException:PKIX路径生成失败：sun.security.provider.certpath.SunCertPathBuilderException:找不到请求目标的有效证书路径
在com.sun.mail.imap.IMAPStore.protocolConnect上（IMAPStore.java:571）
在javax.mail.Service.connect（Service.java:288）
在javax.mail.Service.connect（Service.java:169）
查看mailpackage.Connection.check（Connection.java:63）
在mailpackage.Connection.run处（Connection.java:33）
运行（Thread.java:744）
原因：javax.net.ssl.SSLHandshakeException:sun.security.validator.ValidatorException:PKIX路径生成失败：sun.security.provider.certpath.SunCertPathBuilderException:找不到请求目标的有效证书路径
位于sun.security.ssl.Alerts.getSSLException（Alerts.java:192）
位于sun.security.ssl.SSLSocketImpl.fatal（SSLSocketImpl.java:1884）
位于sun.security.ssl.Handshaker.fatalSE（Handshaker.java:276）
位于sun.security.ssl.Handshaker.fatalSE（Handshaker.java:270）
位于sun.security.ssl.ClientHandshaker.serverCertificate（ClientHandshaker.java:1341）
位于sun.security.ssl.ClientHandshaker.processMessage（ClientHandshaker.java:153）
位于sun.security.ssl.Handshaker.processLoop（Handshaker.java:868）
位于sun.security.ssl.Handshaker.process_记录（Handshaker.java:804）
位于sun.security.ssl.SSLSocketImpl.readRecord（SSLSocketImpl.java:1016）
位于sun.security.ssl.SSLSocketImpl.performInitialHandshake（SSLSocketImpl.java:1312）
位于sun.security.ssl.SSLSocketImpl.readDataRecord（SSLSocketImpl.java:882）
位于sun.security.ssl.AppInputStream.read（AppInputStream.java:102）
位于com.sun.mail.util.TraceInputStream.read（TraceInputStream.java:110）
在java.io.BufferedInputStream.fill处（BufferedInputStream.java:235）
在java.io.BufferedInputStream.read处（BufferedInputStream.java:254）
位于com.sun.mail.iap.ResponseInputStream.readResponse（ResponseInputStream.java:98）
位于com.sun.mail.iap.Response（Response.java:96）
在com.sun.mail.imap.protocol.imapreponse上。（imapreponse.java:61）
在com.sun.mail.imap.protocol.IMAPResponse.readResponse（IMAPResponse.java:135）上
com.sun.mail.imap.protocol.IMAPProtocol.readResponse（IMAPProtocol.java:261）
在com.sun.mail.iap.Protocol.（Protocol.java:114）
在com.sun.mail.imap.protocol.IMAPProtocol.（IMAPProtocol.java:104）
在com.sun.mail.imap.IMAPStore.protocolConnect上（IMAPStore.java:538）
... 还有5个
原因：sun.security.validator.validator异常：PKIX路径生成失败：sun.security.provider.certpath.SunCertPathBuilderException:找不到请求目标的有效证书路径
位于sun.security.validator.PKIXValidator.doBuild（PKIXValidator.java:385）
位于sun.security.validator.PKIXValidator.engineValidate（PKIXValidator.java:292）
位于sun.security.validator.validator.validate（validator.java:260）
位于sun.security.ssl.X509TrustManagerImpl.validate（X509TrustManagerImpl.java:326）
位于sun.security.ssl.X509TrustManagerImpl.checkTrusted（X509TrustManagerImpl.java:231）
位于sun.security.ssl.X509TrustManagerImpl.checkServerTrusted（X509TrustManagerImpl.java:126）
位于sun.security.ssl.ClientHandshaker.serverCertificate（ClientHandshaker.java:1323）
... 23多
原因：sun.security.provider.certpath.SunCertPathBuilderException:找不到请求目标的有效证书路径
位于sun.security.provider.certpath.SunCertPathBuilder.engineBuild（SunCertPathBuilder.java:196）
位于java.security.cert.CertPathBuilder.build（CertPathBuilder.java:268）
位于sun.security.validator.PKIXValidator.doBuild（PKIXValidator.java:380）
... 还有29个

我读了一些关于PKIX路径错误的文章，上面说要将证书作为可信证书添加到java存储中，但我不知道这是否是解决此问题的方法，如果是，我不知道如何执行

//我没有访问邮件服务器的权限

有什么建议吗？谢谢

引用链接站点中的文本：

问：当通过SSL连接到我的邮件服务器时，我遇到了一个异常，比如“找不到请求目标的有效认证路径”

答：您的服务器可能正在使用测试证书或自签名证书，而不是由商业证书颁发机构签名的证书。您需要将服务器的证书安装到信任存储中。InstallCert程序将有所帮助

或者，您可以将“mail.protocol.ssl.trust”属性设置为邮件服务器的主机名。有关详细信息，请参阅协议提供程序包的javadocs

此问题的其他常见原因有：

• 有防火墙或反病毒程序拦截你的请求
• 您的JDK安装中出现了一些错误，使其无法找到可信证书颁发机构的证书
• 您运行的应用程序服务器覆盖了JDK的可信证书颁发机构列表

---

问题解决了

解决办法是：

首先通过openssl从邮件服务器获取自签名证书：

echo | openssl s_client -connect yoursever:port 2>&1 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > yourcert.pem

然后将yourcert.pem文件保存到这个路径/Library/Java/Home/lib/security（在macOSX上）中，并像下面这样将证书文件放入cacerts中

connec=new Connection();
 (new Thread(connec)).start();

keytool -keystore cacerts -importcert -alias youralias -file yourcert.pem

默认密钥库密码是changeit

您可以查看所做的更改

C:\Program Files\Java\jdk1.7.0_79\jre\lib\security

C:\Program Files\Java\jdk1.6.0\jre\lib\security

MailSSLSocketFactory sf = new MailSSLSocketFactory();
sf.setTrustAllHosts(true); 
properties.put("mail.imap.ssl.trust", "*");
properties.put("mail.imap.ssl.socketFactory", sf);