从 Spring.NET xml 配置访问 ConfigurationManager.AppSettings 值

Question

我有一个要求，要求我使用 Spring.net 获取存储在 app.config 中的连接字符串，然后将检索到的连接字符串注入到实例化对象中。

如何使用 Spring.net 的 xml 配置来做到这一点？

例如，而不是我的代码这样做：

// Spring.net config:
<object name="myService" type="com.acme.MyService, com.acme">
    <constructor-arg type="System.String" value="myConnectionName"/>
</object>

// Web.config:
<connectionStrings>
    <add name="myConnectionName" connectionString="DB_connectionstring"/>
</connectionStrings>

// Codes:
public class MyService {
    public MyService(string connectionName) {
        var connectionString = ConfigurationManager.AppSettings[connectionName];
        // use connectionString to create a DB connection, etc
    }
}

我想要这样：

 // Spring.net config:
<object name="myService" type="com.acme.MyService, com.acme">
    <constructor-arg type="System.String" ref="retrievedConnectionString"/>
</object>    
// How to make a call similar to "ConfigurationManager.AppSettings[connectionName]" and get the connection string from Web.config and put inside "retrievedConnectionString"?

// Web.config:
<connectionStrings>
    <add name="myConnectionName" connectionString="DB_connectionstring"/>
</connectionStrings>

// Codes:
public class MyService {
    public MyService(string connectionString) {
        // use connectionString to create a DB connection, etc
    }
}

甚至可以从 Spring.net xml 配置中调用 ConfigurationManager.AppSettings[..] 吗？

Answer 1

过去我使用expression 来实现这一点，但通过这个问题和bbaia 的回答，我发现更好的方法是使用VariablePlaceholderConfigurer。当您使用VariablePlaceholderConfigurer 而不是我的“表达式黑客”时，您不会将自己绑定到变量的appSettings / connectionStrings 样式配置：您可以切换到 spring.net 甚至提供的VariableSources 之一实现你自己的IVariableSource。

开箱即用，Spring.NET 提供 VariablePlaceholderConfigurers 来从标准 .NET 设置中检索变量，例如 AppSettings、ConnectionStrings、UserSettings 和 ApplicationSettings。 bbaia 的回答部分说明了这一点，您将在下面找到一个完整的示例。

“表达式破解”：从 xml 配置调用 ConfigurationManager

所以，我不建议您使用它，但这是我过去使用的 hack，应用于您的配置：

<object object name="myService" type="com.acme.MyService, com.acme">
  <constructor-arg name="Connection" 
                   expression="T(System.Configuration.ConfigurationManager).ConnectionStrings['myConnectionName']" />
</object>

您可以对ConfigurationManager.AppSettings 使用相同的方法，例如：

<object object name="myService" type="com.acme.MyService, com.acme">
  <constructor-arg name="AnotherConstructorArgument" 
                   expression="T(System.Configuration.ConfigurationManager).AppSettings['mySetting']" />
</object>

VariablePlaceholderConfigurer：参考 Spring.NET xml 配置中的 .NET 设置

您可以轻松配置 VariablePlaceholderConfigurer 以从标准 .NET 设置中检索变量，例如 AppSettings、ConnectionStrings、UserSettings 和 ApplicationSettings。例如，考虑这个 xml 配置：

<?xml version="1.0" encoding="utf-8"?>
<objects xmlns="http://www.springframework.net" >

  <object type="Spring.Objects.Factory.Config.VariablePlaceholderConfigurer, Spring.Core">
    <property name="VariableSources">
      <list>
        <object type="Spring.Objects.Factory.Config.ConnectionStringsVariableSource, Spring.Core" />
        <object type="Spring.Objects.Factory.Config.ConfigSectionVariableSource, Spring.Core">
          <!-- Sections to read, sepearated by comma (leave out spaces) -->
          <property name="SectionNames"
                    value="appSettings,applicationSettings/q7991262.Properties.Settings,userSettings/q7991262.Properties.Settings" />
        </object>
      </list>
    </property>
  </object>

  <!-- Note that you have to append '.connectionstring' to the key! -->
  <object id="usingConnectionStringsVariableSource" 
          type="q7991262.MyService, q7991262">
    <property name="Connection" 
              value="${myConnectionName.connectionString}" />
  </object>

  <object id="configSectionVariableSource" 
          type="q7991262.MyService, q7991262">
    <property name="Connection" 
              value="${myConnectionNameAppSettings}" />
  </object>

  <object id="userSettingsSection" 
          type="q7991262.MyService, q7991262">
    <property name="Connection" 
              value="${myConectionNameUserSetting}" />
  </object>

  <object id="applicationSetting" 
          type="q7991262.MyService, q7991262">
    <property name="Connection" 
              value="${myConectionNameApplicationSetting}" />
  </object>

</objects>

它从此app.config读取设置：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
      <section name="q7991262.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false" />
    </sectionGroup>
    <sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
      <section name="q7991262.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
    </sectionGroup>
  </configSections>

  <connectionStrings>
    <add name="myConnectionName" 
         connectionString="From connection string section."/>
  </connectionStrings>

  <appSettings>
    <add key="myConnectionNameAppSettings" 
         value="From app setting section." />
  </appSettings>

  <userSettings>
    <q7991262.Properties.Settings>
      <setting name="myConectionNameUserSetting" serializeAs="String">
        <value>My connection from user settings.</value>
      </setting>
    </q7991262.Properties.Settings>
  </userSettings>

  <applicationSettings>
    <q7991262.Properties.Settings>
      <setting name="myConectionNameApplicationSetting" serializeAs="String">
        <value>My connection from application settings.</value>
      </setting>
    </q7991262.Properties.Settings>
  </applicationSettings>

</configuration>

这些配置取自this working sample at github。

Answer 2

另一种解决方案是使用 VariablePlaceholderConfigurer ： http://www.springframework.net/doc-latest/reference/html/objects.html#objects-variablesource

ConnectionStringsVariableSource 实现允许您从配置文件中的 ConnectionString 部分获取值。

<object type="Spring.Objects.Factory.Config.VariablePlaceholderConfigurer, Spring.Core">
  <property name="VariableSources">
    <list>
      <object type="Spring.Objects.Factory.Config.ConnectionStringsVariableSource, Spring.Core"/>
    </list>
  </property>
</object>

<object name="myService" type="com.acme.MyService, com.acme">
    <constructor-arg type="System.String" value="${myConnectionName.connectionString}"/>
</object>

来自 Spring.NET 论坛的示例： http://forum.springframework.net/showthread.php?3961