经过大量测试，我找到了正确的解决方案.问题在于证书文件声明.

After lots of testing, I found the correct solution. The problem was with the cert file declaration.

我尝试使用捆绑的证书文件(example.com.pem)发送发帖请求

I tried sending the post request using the bundled cert files (example.com.pem)

http.ca_file = File.read(File.join(Rails.root, "/crt/example.com.pem"))

所以，我用每个crt和密钥文件更改了上面的声明

So, I changed the above declaration with the each crt and key files

http.cert = OpenSSL::X509::Certificate.new(File.read(File.join(Rails.root, "/crt/example.com.crt")))
http.key = OpenSSL::PKey::RSA.new(File.read(File.join(Rails.root, "/crt/example.com.key")))
req = Net::HTTP::Post.new(uri.path, initheader = {'Content-Type' =>'application/xml'}).

现在可以了.

完整代码

uri = URI("https://test.compassplus.com:8444/Exec")
xml = "
<TKKPG>
    <Request>
    <Operation>CreateOrder</Operation> 
    <Language></Language>
    <Order>
        <OrderType>Purchase</OrderType>
        <Merchant>99999</Merchant>
        <Amount>10000</Amount>
        <Currency>524</Currency>
        <Description>Tour Purchase</Description>
        <ApproveURL>/approve.html</ApproveURL>
        <CancelURL>/cancel.html</CancelURL>
        <DeclineURL></DeclineURL>
        <email></email>
        <phone></phone>
        <AddParams>
            <FA-DATA></FA-DATA>
            <SenderPostalCode></SenderPostalCode>
            <AcctType></AcctType> 
            <TranAddendums></TranAddendums> 
            <TranAddendumsVISA></TranAddendumsVISA> 
            <TranAddendumsMC></TranAddendumsMC> 
            <TranAddendumsAMEX></TranAddendumsAMEX> 
            <TranAddendumsJCB></TranAddendumsJCB> 
            <OrderExpirationPeriod></OrderExpirationPeriod> 
            <OrigAmount></OrigAmount> 
            <OrigCurrency></OrigCurrency>
        </AddParams>
        <Fee></Fee> 
    </Order>
    </Request>
</TKKPG>
"
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl  = true
http.ssl_version = :TLSv1_2
http.cert = OpenSSL::X509::Certificate.new(File.read(File.join(Rails.root, "/crt/example.com.crt")))
http.key = OpenSSL::PKey::RSA.new(File.read(File.join(Rails.root, "/crt/example.com.key")))
req = Net::HTTP::Post.new(uri.path, initheader = {'Content-Type' =>'application/xml'})
@res = http.request(req, xml)

参考.

HTTP库Ruby是否具有HTTPS，SSL客户端证书和Keep-Alive支持?