如何使用 Tomcat 覆盖 spring 属性参数? [英] How to override spring property param with Tomcat?

问题描述

我已经在 Spring 应用程序中定义了属性.

I have defined property in Spring application.

@Configuration
public class WebappConfiguration {

    @Value("${ext.storage.path}")
    private String extDirectoryPath;

    public String getExtDirectoryPath() {
        return extDirectoryPath;
    }
}

ext.storage.path 属性的默认值在 application.properties 文件中定义.

Default value for ext.storage.path property is defined in application.properties file.

application.properties

ext.storage.path=/home/user/ext/

当我使用 VM 选项 -Dext.storage.path=/var/webapp-data/ 将 WAR 部署到 tomcat 时，此值已成功加载.但我想从每个环境的上下文文件中更智能地加载属性值.

When I deploy WAR to tomcat with VM options -Dext.storage.path=/var/webapp-data/, this value is loaded successfully. But I would like to load property values more smarter from context files for every environment.

所以我把WAR部署到Tomcat的ROOT，WAR文件的名字是ROOT.war，然后分解成ROOT 目录.我在路径 {CATALINA_BASE}/Catalina/localhost/ROOT.xml 上创建了 context 文件，内容如下.

So I deploy the WAR to ROOT of Tomcat, name of WAR file is ROOT.war and it is exploded to ROOT directory. I created context file on path {CATALINA_BASE}/Catalina/localhost/ROOT.xml with following content.

ROOT.xml

<Context 
        docBase="/opt/webapp-tomcat/webapps/ROOT.war"
        path=""
        reloadable="true">

        <Parameter name="ext.storage.path" value="file:/var/webapp-data/" override="true"/>

</Context>

不幸的是，参数没有按照方式加载，它具有来自application.properties的默认值.

Unfortunately, the param is not loaded according to the way, it has default value from application.properties.

经过一番调查，我将Parameter放入Tomcat的主context.xml文件中，并覆盖了该值.

After a little investigation, I put the Parameter into main context.xml file of Tomcat and the value is overridden.

<Parameter name="ext.storage.path" value="file:/var/webapp-data/" override="true"/> 

推荐答案

我所知道的最好的技术是将特定于环境的内容放入 Tomcat 的 conf/context.xml 文件中.

The best technique I know of is to put environment-specific stuff into Tomcat's conf/context.xml file.

  <Environment name="myApp/extStoragePath" type="java.lang.String" value="/var/data/myapp"/>

这定义了一个 JNDI 变量，您可以使用以下内容在代码中查找该变量:

This defines a JNDI variable that you lookup in your code with something like this:

Context initCtx = new InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
String extStoragePath = (String) envCtx.lookup("myApp/extStoragePath");

您也可以使用这种技术来加载复杂的对象，如数据库数据源等.它具有巨大的优势:

You can also use this technique to load complex objects like database datasources etc. It has huge advantages:

• 配置是针对环境的，而不是针对应用程序的
• 您无需弄乱 Tomcat 启动脚本
• 相同的二进制文件无需修改即可在 DEV、UAT 和 PROD 中运行.这大大简化了构建过程.

此外，Spring 提供了一个 org.springframework.jndi.JndiObjectFactoryBean，它可以从您的 Spring 配置文件访问 JNDI.

Also, Spring provides a org.springframework.jndi.JndiObjectFactoryBean which can access JNDI from your spring configuration files.

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