在Classic ASP中使用Paypal REST API

在Classic ASP中使用PayPal REST API

基础概念

PayPal REST API是PayPal提供的现代支付接口，允许开发者通过HTTP请求与PayPal系统交互，处理支付、退款、订阅等交易。Classic ASP(Active Server Pages)是微软早期的服务器端脚本技术，虽然较老但仍在使用。

主要挑战

由于Classic ASP是较老的技术，而PayPal REST API是现代API，主要挑战包括：

Classic ASP原生不支持JSON处理
缺乏现代HTTP客户端功能
没有内置的OAuth 2.0支持

解决方案

1. 设置基础环境

首先需要确保服务器支持HTTPS请求和JSON处理。

<%
' 设置PayPal API端点
Const PAYPAL_API_SANDBOX = "https://api.sandbox.paypal.com"
Const PAYPAL_API_LIVE = "https://api.paypal.com"

' 选择环境
Dim paypalApiUrl
paypalApiUrl = PAYPAL_API_SANDBOX ' 测试环境
' paypalApiUrl = PAYPAL_API_LIVE ' 生产环境

' 你的PayPal客户端ID和密钥
Const CLIENT_ID = "你的客户端ID"
Const CLIENT_SECRET = "你的客户端密钥"
%>

2. 获取访问令牌

PayPal REST API使用OAuth 2.0认证，需要先获取访问令牌。

<%
Function GetPayPalAccessToken()
    Dim http, url, postData, responseText, json
    
    Set http = Server.CreateObject("MSXML2.ServerXMLHTTP")
    url = paypalApiUrl & "/v1/oauth2/token"
    
    ' 准备请求数据
    postData = "grant_type=client_credentials"
    
    ' 设置请求头
    http.Open "POST", url, False
    http.setRequestHeader "Authorization", "Basic " & Base64Encode(CLIENT_ID & ":" & CLIENT_SECRET)
    http.setRequestHeader "Content-Type", "application/x-www-form-urlencoded"
    http.setRequestHeader "Accept", "application/json"
    
    ' 发送请求
    http.Send postData
    
    ' 处理响应
    responseText = http.responseText
    
    ' 解析JSON响应 - 需要JSON解析库或自定义函数
    Set json = ParseJson(responseText)
    
    GetPayPalAccessToken = json("access_token")
    
    Set http = Nothing
End Function

' Base64编码函数
Function Base64Encode(text)
    Dim xml, node
    Set xml = Server.CreateObject("MSXML2.DOMDocument")
    Set node = xml.createElement("b64")
    node.DataType = "bin.base64"
    node.nodeTypedValue = Stream_StringToBinary(text)
    Base64Encode = node.text
    Set node = Nothing
    Set xml = Nothing
End Function

Function Stream_StringToBinary(text)
    Dim stream
    Set stream = Server.CreateObject("ADODB.Stream")
    stream.Type = 2 ' adTypeText
    stream.Charset = "utf-8"
    stream.Open
    stream.WriteText text
    stream.Position = 0
    stream.Type = 1 ' adTypeBinary
    stream.Position = 0
    Stream_StringToBinary = stream.Read
    Set stream = Nothing
End Function
%>

3. 创建支付

获取访问令牌后，可以创建支付请求。

<%
Function CreatePayPalPayment(amount, currency, description, returnUrl, cancelUrl)
    Dim http, url, postData, responseText, json, accessToken
    
    ' 获取访问令牌
    accessToken = GetPayPalAccessToken()
    
    Set http = Server.CreateObject("MSXML2.ServerXMLHTTP")
    url = paypalApiUrl & "/v1/payments/payment"
    
    ' 准备JSON请求数据
    postData = "{"
    postData = postData & """intent"":""sale"","
    postData = postData & """payer"":{""payment_method"":""paypal""},"
    postData = postData & """transactions"":[{"
    postData = postData & """amount"":{"
    postData = postData & """total"":""" & amount & ""","
    postData = postData & """currency"":""" & currency & """"
    postData = postData & "},"
    postData = postData & """description"":""" & description & """"
    postData = postData & "}],"
    postData = postData & """redirect_urls"":{"
    postData = postData & """return_url"":""" & returnUrl & ""","
    postData = postData & """cancel_url"":""" & cancelUrl & """"
    postData = postData & "}"
    postData = postData & "}"
    
    ' 设置请求头
    http.Open "POST", url, False
    http.setRequestHeader "Authorization", "Bearer " & accessToken
    http.setRequestHeader "Content-Type", "application/json"
    http.setRequestHeader "Accept", "application/json"
    
    ' 发送请求
    http.Send postData
    
    ' 处理响应
    responseText = http.responseText
    
    ' 解析JSON响应
    Set json = ParseJson(responseText)
    
    ' 返回支付链接
    For Each link In json("links")
        If link("rel") = "approval_url" Then
            CreatePayPalPayment = link("href")
            Exit For
        End If
    Next
    
    Set http = Nothing
End Function
%>

4. 执行支付

用户批准后执行支付：

<%
Function ExecutePayPalPayment(paymentId, payerId)
    Dim http, url, postData, responseText, json, accessToken
    
    ' 获取访问令牌
    accessToken = GetPayPalAccessToken()
    
    Set http = Server.CreateObject("MSXML2.ServerXMLHTTP")
    url = paypalApiUrl & "/v1/payments/payment/" & paymentId & "/execute"
    
    ' 准备JSON请求数据
    postData = "{""payer_id"":""" & payerId & """}"
    
    ' 设置请求头
    http.Open "POST", url, False
    http.setRequestHeader "Authorization", "Bearer " & accessToken
    http.setRequestHeader "Content-Type", "application/json"
    http.setRequestHeader "Accept", "application/json"
    
    ' 发送请求
    http.Send postData
    
    ' 处理响应
    responseText = http.responseText
    
    ' 解析JSON响应
    Set json = ParseJson(responseText)
    
    ' 返回支付状态
    ExecutePayPalPayment = json("state")
    
    Set http = Nothing
End Function
%>

JSON处理

Classic ASP没有内置JSON解析器，需要添加JSON解析功能：

<%
' 简单的JSON解析函数
Function ParseJson(jsonText)
    Dim dict, matches, match, key, value, i
    Set dict = Server.CreateObject("Scripting.Dictionary")
    
    ' 使用正则表达式提取键值对
    Dim regex
    Set regex = New RegExp
    regex.Pattern = """([^""]+)""\s*:\s*(""[^""]*""|\d+|true|false|null)"
    regex.Global = True
    
    Set matches = regex.Execute(jsonText)
    
    For Each match In matches
        key = Mid(match.SubMatches(0), 1)
        value = match.SubMatches(1)
        
        ' 去除字符串值的引号
        If Left(value, 1) = """" Then
            value = Mid(value, 2, Len(value) - 2)
        End If
        
        dict.Add key, value
    Next
    
    Set ParseJson = dict
    Set regex = Nothing
End Function
%>

完整示例

<%
' 创建支付示例
Dim paymentUrl, amount, currency, description, returnUrl, cancelUrl

amount = "10.00"
currency = "USD"
description = "测试支付"
returnUrl = "http://yourdomain.com/success.asp"
cancelUrl = "http://yourdomain.com/cancel.asp"

paymentUrl = CreatePayPalPayment(amount, currency, description, returnUrl, cancelUrl)

If paymentUrl <> "" Then
    Response.Redirect paymentUrl
Else
    Response.Write "创建支付失败"
End If
%>