集成Data Annotations到WCF实现验证

       前面一篇文章，我们介绍了使用Enterprise Libary VAB来实现WCF参数验证。你有可能感觉Enterpise Library 太重量级了，是的，现在我们还要可以借助Data Annotations来实现轻量级解决方案，它曾用于Asp.net MVC等应用程序中，您可能比较熟悉。它们是集成于.net framework。这里我们关键是要实现IParameterInspector接口, 下面是一部分的核心代码:

public class ValidatingParameterInspector: IParameterInspector
    {
        private readonly IEnumerable<IObjectValidator> _validators;
        private readonly IErrorMessageGenerator _errorMessageGenerator;

        public ValidatingParameterInspector(IEnumerable<IObjectValidator> validators, IErrorMessageGenerator errorMessageGenerator)
        {
            ValidateArguments(validators, errorMessageGenerator);

            _validators = validators;
            _errorMessageGenerator = errorMessageGenerator;
        }

        public void AfterCall(string operationName, object[] outputs, object returnValue, object correlationState)
        {
        }

        public object BeforeCall(string operationName, object[] inputs)
        {
            var validationResults = new List<ValidationResult>();

            foreach (var input in inputs)
            {
                foreach (var validator in _validators)
                {
                    var results = validator.Validate(input);
                    validationResults.AddRange(results);
                }
            }

            if (validationResults.Count > 0)
            {
                throw new FaultException(_errorMessageGenerator.GenerateErrorMessage(operationName, validationResults));
            }

            return null;
        }

        private static void ValidateArguments(IEnumerable<IObjectValidator> validators, IErrorMessageGenerator errorMessageGenerator)
        {
            if (validators == null)
            {
                throw new ArgumentNullException("validators");
            }

            if (!validators.Any())
            {
                throw new ArgumentException("At least one validator is required.");
            }

            if (errorMessageGenerator == null)
            {
                throw new ArgumentNullException("errorMessageGenerator");
            }
        }
    }

在CodePlex上有一个WCF Data Annotations开源项目就是解决这个问题。下面我们来看如何使用:

    [ServiceContract]
    public interface IService1
    {
        [OperationContract]
        string GetData(int value);

        [OperationContract]
        CompositeType GetDataUsingDataContract(CompositeType composite);
    }

Service对应的DataContract，您可以看到我们标记[Required]和[StringLength]验证。

    [DataContract]
    public class CompositeType
    {
        bool boolValue = true;
        string stringValue = string.Empty;

        [DataMember]
        [Required]
        public bool BoolValue
        {
            get { return boolValue; }
            set { boolValue = value; }
        }

        [DataMember]
        [Required]
        [StringLength(500, MinimumLength = 5)]
        public string StringValue
        {
            get { return stringValue; }
            set { stringValue = value; }
        }
    }

实现在Service的代码如下:

    //[ValidateDataAnnotationsBehavior]
    public class Service1 : IService1
    {
        public string GetData(int value)
        {
            return string.Format("You entered: {0}", value);
        }

        public CompositeType GetDataUsingDataContract(CompositeType composite)
        {
            if (composite == null)
            {
                throw new ArgumentNullException("composite");
            }
            if (composite.BoolValue)
            {
                composite.StringValue += "Suffix";
            }
            return composite;
        }
    }

如果您使用配置文件就不需要标注ValidateDataAnnotationsBehaviorAttribute了:

  <system.serviceModel>

    <extensions>

      <behaviorExtensions>

        <add name="validateDataAnnotationsBehavior"

             type="DevTrends.WCFDataAnnotations.ValidateDataAnnotationsBehaviorExtensionElement, DevTrends.WCFDataAnnotations, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />

      </behaviorExtensions>

    </extensions>

    <behaviors>

      <serviceBehaviors>

        <behavior>

         <validateDataAnnotationsBehavior/>

          <serviceMetadata httpGetEnabled="True"/>

          <serviceDebug includeExceptionDetailInFaults="False" />

        </behavior>

      </serviceBehaviors>

    </behaviors>

  </system.serviceModel>

我们来写一些基于xunit的单元测试 来验证它们：

    /// <summary>
    /// Wcf unit testing for  http://localhost:17347/WcfService.svc
    /// </summary>
    public class WcfTestingWCFDataAnnotations
    {
        [Fact]
        public void Should_Arise_Validation_Exception_With_ShortString()
        {
            var client = new Service1Client();
            var composetype = new CompositeType
            {
                BoolValue = true,
                StringValue = "two"
            };

            var exception = Assert.Throws<FaultException>(
    () => { var result = client.GetDataUsingDataContract(composetype); }
);
            Assert.Equal(
                @"Service operation GetDataUsingDataContract failed due to validation errors:

StringValue: The field  must be a string with a minimum length of 5 and a maximum length of 500.
",
            exception.Message);

        }

        [Fact]
        public void Should_Get_CorrectString()
        {
            var client = new Service1Client();
            var composetype = new CompositeType
            {
                BoolValue = true,
                StringValue = "twothree"
            };
             var result=client.GetDataUsingDataContract(composetype);
             composetype.StringValue += "Suffix";
             Assert.Equal(composetype.StringValue, result.StringValue);
        }
    }

您还可以使DataContract实现IValidatableObject接口 达到验证的效果：

    [DataContract]
    public class CompositeType : IValidatableObject
    {
        bool boolValue = true;
        string stringValue = string.Empty;

        [DataMember]
        public bool BoolValue
        {
            get { return boolValue; }
            set { boolValue = value; }
        }

        [DataMember]
        public string StringValue
        {
            get { return stringValue; }
            set { stringValue = value; }
        }

        public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
        {
            if (StringValue.Length < 5)
            {
                yield return new ValidationResult("StringValue must be greater than 5", new[] { "StringValue" });
            }
        }
    }

这是一个简单示例，希望对您WCF开发有帮助。

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作者：Petter Liu
出处：http://www.cnblogs.com/wintersun/
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。
该文章也同时发布在我的独立博客中-Petter Liu Blog。