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如何在 Java 中使用 Spring MVC 'singleton' Scope 讀取 config.properties 值？

已發表: 2018-08-29
Spring MVC 單例範圍教程 - Crunchify

前段時間我寫了一篇關於如何以傳統方式讀取配置文件的教程。 但是如果你想將它作為一個 Spring MVC 框架加載呢？

最常見的情況是，您可能需要一直訪問 Java 類中的一些config.properties值。 有一種簡單的方法可以使用 Spring MVC 的單例範圍來獲取它。

請看下面完整的工作區圖片。

我們需要創建4個文件：

  1. com.crunchify.tutorial 包下的com.crunchify.tutorial
  2. /go/config/文件夾下的 config.properties 文件
  3. /resources文件夾下的 spring-bean.xml 文件
  4. pom.xml 文件（將項目轉換為 Maven 項目）
Eclipse 項目結構 - Crunchify Spring MVC - 加載配置

讓我們開始吧：

第1步

創建名為CrunchifyLoadPropertiesSpringMVC動態 Web 項目

創建新的動態 Web 項目 - Crunchify

第2步

將項目轉換為 Maven 項目。

這將創建pom.xml文件，我們將添加 Spring 依賴項。

創建 Maven POM 項目 - Crunchify

第三步

創建文件 CrunchifySpringExample.java

Java
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package com . crunchify . tutorial ;
 
import org . springframework . beans . factory . annotation . Autowired ;
import org . springframework . beans . factory . annotation . Value ;
import org . springframework . context . annotation . Scope ;
import org . springframework . context . support . ClassPathXmlApplicationContext ;
import org . springframework . stereotype . Component ;
 
/**
*
* @author Crunchify.com
*/
 
@Component ( "crunchifySpringExample" )
@Scope ( "singleton" )
public class CrunchifySpringExample {
 
     private static boolean springExample ;
     private static String springTutorial ;
     private static String url ;
 
     @Autowired
     public CrunchifySpringExample ( @Value ( "${CRUNCHIFY_URL}" ) String url , @Value ( "${SPRING_TUTORIAL}" ) String springTutorial ,
             @Value ( "${IS_THIS_SPRING_EXAMPLE}" ) boolean springExample ) {
         CrunchifySpringExample . springExample = springExample ;
         CrunchifySpringExample . springTutorial = springTutorial ;
         CrunchifySpringExample . url = url ;
 
     }
 
     @SuppressWarnings ( { "resource" , "unused" } )
     public static void main ( String [ ] args ) {
         try {
             ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext ( new String [ ] { "spring-bean.xml" } ) ;
         } catch ( Throwable e ) {
             System . out . println ( e ) ;
         }
 
         System . out . println ( "\nLoading Properties from Config File during application startup: \n\nSPRING_TUTORIAL: " + springTutorial ) ;
         System . out . println ( "IS_THIS_SPRING_EXAMPLE: " + springExample ) ;
         System . out . println ( "CRUNCHIFY_URL: " + url ) ;
     }
 
}

第四步

這是我的pom.xml文件。

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< project xmlns = "http://maven.apache.org/POM/4.0.0" xmlns : xsi = "http://www.w3.org/2001/XMLSchema-instance"
     xsi : schemaLocation = "http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" >
     < modelVersion > 4.0.0 < / modelVersion >
     < groupId > CrunchifyLoadPropertiesSpringMVC < / groupId >
     < artifactId > CrunchifyLoadPropertiesSpringMVC < / artifactId >
     < version > 0.0.1 - SNAPSHOT < / version >
     < packaging > war < / packaging >
     < name > CrunchifyLoadPropertiesSpringMVC < / name >
     < build >
         < sourceDirectory > src < / sourceDirectory >
         < plugins >
             < plugin >
                 < artifactId > maven - compiler - plugin < / artifactId >
                 < version > 3.1 < / version >
                 < configuration >
                     < source > 1.7 < / source >
                     < target > 1.7 < / target >
                 < / configuration >
             < / plugin >
             < plugin >
                 < artifactId > maven - war - plugin < / artifactId >
                 < version > 2.3 < / version >
                 < configuration >
                     < warSourceDirectory > WebContent < / warSourceDirectory >
                     < failOnMissingWebXml > false < / failOnMissingWebXml >
                 < / configuration >
             < / plugin >
         < / plugins >
     < / build >
 
     < properties >
         < project . build . sourceEncoding > UTF - 8 < / project . build . sourceEncoding >
         < spring . version > 4.0.2.RELEASE < / spring . version >
     < / properties >
 
     < dependencies >
 
         < ! -- Spring base -- >
         < dependency >
             < groupId > org . springframework < / groupId >
             < artifactId > spring - aop < / artifactId >
             < version > $ { spring . version } < / version >
             < exclusions >
                 < exclusion >
                     < groupId > commons - logging < / groupId >
                     < artifactId > commons - logging < / artifactId >
                 < / exclusion >
             < / exclusions >
         < / dependency >
         < ! -- Spring MVC -- >
         < dependency >
             < groupId > org . springframework < / groupId >
             < artifactId > spring - webmvc < / artifactId >
             < version > $ { spring . version } < / version >
         < / dependency >
         < dependency >
             < groupId > org . springframework < / groupId >
             < artifactId > spring - web < / artifactId >
             < version > $ { spring . version } < / version >
         < / dependency >
         < dependency >
             < groupId > commons - logging < / groupId >
             < artifactId > commons - logging < / artifactId >
             < version > 1.1.1 < / version >
         < / dependency >
     < / dependencies >
< / project >

第 5 步

如果您沒有看到“ resources ”文件夾。 創建一個。

創建資源文件夾 - Crunchify Spring 示例

第 6 步

使用以下內容創建config.properties文件。

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# Crunchify Properties
IS_THIS_SPRING_EXAMPLE = true
SPRING_TUTORIAL = CRUNCHIFY_TUTORIAL
CRUNCHIFY_URL = https : //crunchify.com

第 7 步

spring-bean.xml文件內容

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<? xml version = "1.0" encoding = "UTF-8" ?>
< beans xmlns = "http://www.springframework.org/schema/beans"
     xmlns : util = "http://www.springframework.org/schema/util" xmlns : xsi = "http://www.w3.org/2001/XMLSchema-instance"
     xmlns : context = "http://www.springframework.org/schema/context"
     xsi : schemaLocation = "
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
       http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context-3.0.xsd" >
 
     < util : properties id = "nodeProperty"
         location = "classpath:config/config.properties" / >
     < context : property - placeholder
         properties - ref = "nodeProperty" / >
     < context : component - scan base - package = "com.crunchify.tutorial" / >
< / beans >

步驟 8

現在運行CrunchifySpringExample.java ，你應該會看到這樣的結果。

第 9 步

輸出

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Jul 05 , 2014 3 : 38 : 52 PM org . springframework . context . support . AbstractApplicationContext prepareRefresh
INFO : Refreshing org . springframework . context . support . ClassPathXmlApplicationContext @ 7e3bfb66 : startup date [ Sat Jul 05 15 : 38 : 52 CDT 2014 ] ; root of context hierarchy
Jul 05 , 2014 3 : 38 : 52 PM org . springframework . beans . factory . xml . XmlBeanDefinitionReader loadBeanDefinitions
INFO : Loading XML bean definitions from class path resource [ spring - bean . xml ]
Jul 05 , 2014 3 : 38 : 52 PM org . springframework . core . io . support . PropertiesLoaderSupport loadProperties
INFO : Loading properties file from class path resource [ config / config . properties ]
 
Loading Properties from Config File during application startup :
 
SPRING_TUTORIAL : CRUNCHIFY_TUTORIAL
IS_THIS_SPRING_EXAMPLE : true
CRUNCHIFY_URL : https : //crunchify.com

享受和快樂編碼..