Question

我们有一个连接到数据库的WCF REST服务。实际上，我们有几个数据库实例，都具有相同的模式。

我们希望为每个数据库实例设置一个端点，并将连接字符串与端点相关联。该服务将读取连接字符串并连接到相应的SQL Server实例。

我确信这是可能的;这是个好主意吗？我该如何设置？ MSDN上有文档吗？

修改：我找到this question，答案建议在标头中添加客户端的连接信息。出于安全原因，我不想这样做，因为我做想要为每个数据库设置一个独特的uri。

Answer 1

这比我想象的要困难一些。 WCF有这么多扩展点，很难选择正确的。如果您认为有更好的方法，或者有任何问题，请回答或评论。

我已经决定使用实现IEndpointBehavior和IDispatchMessageInspector的自定义类。我有一个派生自BehaviorExtensionElement的类，它允许我将行为与配置中的端点相关联。 This blog post描述了hot do do that。

我的DatabaseConnectionContext课程如下：

/// <summary>
/// An endpoint behavior that associates a database connection string name with the endpoint and adds it to the
/// properties of incoming messages.
/// </summary>
public class DatabaseConnectionContext : IEndpointBehavior, IDispatchMessageInspector
{
    /// <summary>
    /// Initializes a new instance of the <see cref="DatabaseConnectionContext"/> class with the provided connection string name.
    /// </summary>
    /// <param name="connectionStringName">The name of the connection string to associate with the endpoint.</param>
    public DatabaseConnectionContext(string connectionStringName)
    {
        this.ConnectionStringName = connectionStringName;
    }

    /// <summary>
    /// Gets the name of the connection string to associate with the endpoint.
    /// </summary>
    public string ConnectionStringName { get; private set; }

    /// <inheritdoc />
    public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
    {
    }

    /// <inheritdoc />
    public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
    {
        throw new NotImplementedException();
    }

    /// <inheritdoc />
    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {
        endpointDispatcher.DispatchRuntime.MessageInspectors.Add(this);
    }

    /// <inheritdoc />
    public void Validate(ServiceEndpoint endpoint)
    {
    }

    /// <inheritdoc />
    public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
    {
        request.Properties["connectionStringName"] = this.ConnectionStringName;
        return null;
    }

    /// <inheritdoc />
    public void BeforeSendReply(ref Message reply, object correlationState)
    {
    }
}

在我的服务类中，我有这个方法：

    /// <summary>
    /// Returns the connection string to use for this service call.
    /// </summary>
    /// <returns>A SQL Server database connection string.</returns>
    private string GetConnectionString()
    {
        string connectionStringName = (string)OperationContext.Current.IncomingMessageProperties["connectionStringName"];
        return ConfigurationManager.ConnectionStrings[connectionStringName].ConnectionString;
    }

我的BehaviorExtensionElement课程如下：

/// <summary>
/// Associates a <see cref="DatabaseConnectionContext"/> with an endpoint in configuration.
/// </summary>
public class DatabaseConnectionContextBehaviorExtension : BehaviorExtensionElement
{
    /// <summary>
    /// The name of the <see cref="ConnectionStringName"/> property when it appears in a configuration file.
    /// </summary>
    private const string ConnectionStringNamePropertyName = "connectionStringName";

    /// <summary>
    /// Gets or sets the name of the configuration string to associate with the endpoint.
    /// </summary>
    [ConfigurationProperty(ConnectionStringNamePropertyName)]
    public string ConnectionStringName
    {
        get
        {
            return (string)this[ConnectionStringNamePropertyName];
        }

        set
        {
            this[ConnectionStringNamePropertyName] = value;
        }
    }

    /// <inheritdoc />
    public override Type BehaviorType
    {
        get { return typeof(DatabaseConnectionContext); }
    }

    /// <inheritdoc />
    protected override object CreateBehavior()
    {
        return new DatabaseConnectionContext(this.ConnectionStringName);
    }
}

我的web.config包含以下内容：

<behaviors>

  <endpointBehaviors>
    <behavior name="DevRestEndpointConfiguration">
      <webHttp helpEnabled="false" />
      <connectionStringInterceptor connectionStringName="myDevConnectionStringName" />
    </behavior>
    <behavior name="ProductionRestEndpointConfiguration">
      <webHttp helpEnabled="false" />
      <connectionStringInterceptor connectionStringName="myProductionConnectionStringName" />
    </behavior>
  </endpointBehaviors>

</behaviors>

<extensions>
  <behaviorExtensions>
    <add name="connectionStringInterceptor" type="DatabaseConnectionContextBehaviorExtension, MyAssembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
  </behaviorExtensions>
</extensions>

<endpoint />部分中的每个<services />元素都将behaviorConfiguration设置为<endpointBehaviors />部分中相应元素的名称。

Answer 2

为什么不添加一个新参数来指定调用将连接的数据库？

例如：

您可以添加db参数，这些参数将获得一个数字，然后您将连接
您可以在身份验证方法

作为第一项的示例：

public ProductItem GetProduct(int productId, int db = 1)
{
    ProductItem product = new ProductItem();
    string connectionString = getConnectionStringForDb(db);

    using (SqlConnection connection =
        new SqlConnection(connectionString))
    {
        SqlCommand command = new SqlCommand("SELECT name, price FROM Products WHERE productId = @product;", connection);
        command.Parameters.AddWithValue("@product", productId);

        try
        {
            connection.Open();
            SqlDataReader reader = command.ExecuteReader();
            reader.Read();

            product = new product({
                Name = reader[0],
                Price = reader[1]
            });

            reader.Close();
        }
        catch (Exception ex)
        {
            // Log exception
        }
    }

    return product;
}

采取from MSDN

private string getConnectionStringForDb(int type)
{

    System.Configuration.ConnectionStringSettings connString;
    System.Configuration.Configuration rootWebConfig = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("/MyWebSiteRoot");

    if (rootWebConfig.ConnectionStrings.ConnectionStrings.Count > 0) {

        connString = rootWebConfig.ConnectionStrings.ConnectionStrings["DBConnectionString_" + type];

        if (connString == null) {
            // LOG ERROR
        }
    }
    return connString.ConnectionString;
}

然后只需在web.config中添加连接字符串，然后输入名称：

DBConnectionString_1, DBConnectionString_2, DBConnectionString_3

或任何对你有意义的事情。

<connectionStrings>
  <add 
    name="DBConnectionString_1" 
    connectionString="Data Source=serverName;Initial 
    Catalog=Northwind;Persist Security Info=True;User 
    ID=userName;Password=password"
    providerName="System.Data.SqlClient"
  />
  <add 
    name="DBConnectionString_2" 
    connectionString="Data Source=serverName;Initial 
    Catalog=Northwind;Persist Security Info=True;User 
    ID=userName;Password=password"
    providerName="System.Data.SqlClient"
  />
  <add 
    name="DBConnectionString_3" 
    connectionString="Data Source=serverName;Initial 
    Catalog=Northwind;Persist Security Info=True;User 
    ID=userName;Password=password"
    providerName="System.Data.SqlClient"
  />
</connectionStrings>

Answer 3

在你的web.config中使用它：

<configuration>

  <appSettings>
    <add key="Foo.svc" value="tagvalue1"/>
  </appSettings>
  ...

您可以通过以下方式在运行时检索值：

    private static string GetConfigValue()
    {
        ServiceEndpointCollection ec = OperationContext.Current
            .Host.Description.Endpoints;
        if (ec!=null)
        {
            var segments = ec[0].Address.ToString().Split('/');
            var s = segments[segments.Length-1]; // "Foo.svc"
            return ConfigurationManager.AppSettings[s]; // "tagvalue1"
        } 
        return null;
    }

我可以将连接字符串与WCF中的端点关联吗？

3 个答案: