在创建 Spring 应用程序上下文之前阅读 application.properties

Question

作为 Spring Boot 项目的一部分，我试图在创建 Spring ApplicationContext 之前读取 application.properties，如下所示，主类package com.example.demo;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.context.ApplicationContext;@SpringBootApplicationpublic class DemoApplication {    public static void main(String[] args) {        ConfigurationClass con = new ConfigurationClass();        con.readProperties();        ApplicationContext c = SpringApplication.run(DemoApplication.class, args);    }}配置类，package com.example.demo;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.PropertySource;import org.springframework.core.env.Environment;@Configuration@PropertySource("classpath:application.properties")public class ConfigurationClass {    private String value1;    private String value2;    @Autowired    private Environment env;    public void readProperties() {        value1 = env.getProperty("app.value1");        value2 = env.getProperty("app.value2");    }    public String getValue1() {        return value1;    }    public String getValue2() {        return value2;    }}我想从 application.properties 中获取一些基本值并进行一些配置。这段代码发生的事情是它抛出一个nullpointerexceptionsince envis null during value1 = env.getProperty("app.value1");。我在这里做错了什么？在创建 springapplication 上下文之前的这个时间点，我如何读取 application.properties 中的值？任何帮助，将不胜感激！

Answer 1

   @Configuration

    @PropertySource("classpath:application.properties")

    public class ConfigurationClass {

        @Value("${app.value1}")    

        private String value1;

        @Value("${app.value2}")    

        private String value2;

        public String getValue1() {

        return value1;

        }

        public String getValue2() {

        return value2;

       }

 }

然后调用它

 @SpringBootApplication

public class DemoApplication {

   public static void main(String[] args) {

    ApplicationContext c = SpringApplication.run(DemoApplication.class, args);

    ConfigurationClass  con = c.getBean(ConfigurationClass.class);

    System.out.println(con.getValue1());

    System.out.println(con.getValue2());

     }

}