播放 2.5.3:使用依赖注入获取配置值 [英] Play 2.5.3: Using dependency injection to get configuration values

问题描述

我正在尝试将 Playframework 应用程序从 2.4 迁移到 2.5.3，但在从 application.conf 文件中获取值时遇到问题:

I'm trying to migrate a Playframework application from 2.4 to 2.5.3 and I have problems to get values from application.conf file:

之前从 application.conf 获取值我所做的是:

Before to get a value of from application.conf what I do was:

Play.application().configuration().getString("label")

现在，因为 Play.application() 已被弃用，我应该使用依赖注入.基于框架文档，我使用以下说明:

Now as Play.application() is deprecated, I should use Dependency injection. Based on the framework documentation I use the following instructions:

1. 定义导入:import javax.inject.*;import play.Configuration;
2. 定义类属性:@Inject 私有配置配置；
3. 在我的类上使用配置类属性

1. Define import: import javax.inject.*; import play.Configuration;
2. Define class property: @Inject private Configuration configuration;
3. Use the configuration class property on my class

当我在控制器 Application.java 上按照这些说明操作时，它运行良好:

When I follow these instructions on my controller Application.java it is working perfectly:

但是当我尝试在我的项目中的其他类对象上使用它时，依赖注入不起作用并且我总是得到一个 NullPointerException.

But when I try to use it on an other class object from my project, the dependency injection is not working and I always get a NullPointerException.

谁能举个例子告诉我如何使用依赖注入从 application.conf 获取值?

Can someone give me an example about how to get values from application.conf using dependency Injection?

我尝试使用 DI 的 Java 代码的某些部分:

Some part of my java code where I try to use the DI:

import javax.inject.Inject;
import play.Configuration;
import play.Logger;

public class Zipper {

    @Inject private  Configuration configuration;

    public void unZip(String zipFilePath) {
        Logger.debug("Display : zipFilePath"+zipFilePath);
        Logger.debug("before call parameter from application.conf");
        Logger.debug("configuration.getString = "+configuration.getString("Unzipedfile.path"));
        Logger.debug("aftercall parameter from application.conf");
    }
}

而且我总是得到一个空指针异常，在 configuration.getString("Unzipedfile.path")

And I always get a null pointer exception, at the line with configuration.getString("Unzipedfile.path")

推荐答案

我把答案放在这里，为了帮助任何有同样问题的人

I put here the answer, in order to help anyone with the same issue

我的错误来自于我以前从调用类实例化 Zipper Java 类的方式.

My error came from the way i used to instantiate my Zipper java class from my calling class.

感谢 Igmar Palsenberg，他给了我答案:https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!topic/play-framework/uLFqTM9_Iy4

Thx to Igmar Palsenberg, he provided me the answer : https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!topic/play-framework/uLFqTM9_Iy4

我使用 Zipper zipTest = new Zipper(); 来实例化我的 Zipper 类，我必须使用 Zipper zipTest = injector.instanceOf(Zipper.class);

I used Zipper zipTest = new Zipper(); to instanciate my Zipper class and i have to use Zipper zipTest = injector.instanceOf(Zipper.class);

这篇关于播放 2.5.3:使用依赖注入获取配置值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！