从类路径加载属性文件时出现奇怪的问题

Question

我创建了这个测试应用程序来解释我遇到的问题。

我有两个具有相同键的属性文件，并且在类路径中共有三个属性文件。

1.mysql.properties

2.vertica.properties

3.other.properties

运行该应用程序时出现以下错误。

Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'mysql-username' in value "${mysql-username}"

这是代码。

package com.test.demo;

import java.util.ArrayList;
import java.util.List;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

@Configuration
@ComponentScan
public class DemoApplication {

    public static void main(String[] args) {
        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(DemoApplication.class);
        MyController bean = applicationContext.getBean(MyController.class);
        bean.log();
    }

    @Bean
    public PropertyPlaceholderConfigurer otherProps() {
        final PropertyPlaceholderConfigurer ppc = new PropertyPlaceholderConfigurer();
        ppc.setIgnoreResourceNotFound(true);

        final List<Resource> resourceList = new ArrayList<>();

        resourceList.add(getOtherResourceFile());

        ppc.setLocations(resourceList.toArray(new Resource[]{}));

        return ppc;
    }

    @Bean
    public PropertyPlaceholderConfigurer verticaProps() {
        final PropertyPlaceholderConfigurer ppc = new PropertyPlaceholderConfigurer();
        ppc.setIgnoreResourceNotFound(true);
        ppc.setPlaceholderPrefix("${vertica-");

        final List<Resource> resourceList = new ArrayList<>();

        resourceList.add(getVerticaResourceFile());

        ppc.setLocations(resourceList.toArray(new Resource[]{}));

        return ppc;
    }

    @Bean
    public PropertyPlaceholderConfigurer mysqlProps() {
        final PropertyPlaceholderConfigurer ppc = new PropertyPlaceholderConfigurer();
        ppc.setIgnoreResourceNotFound(true);
        ppc.setPlaceholderPrefix("${mysql-");
        final List<Resource> resourceList = new ArrayList<>();

        resourceList.add(getDatabasePropertiesFile());

        ppc.setLocations(resourceList.toArray(new Resource[]{}));

        return ppc;
    }

    private Resource getOtherResourceFile() {
        Resource resource = new ClassPathResource("other.properties");
        return resource;
    }

    private Resource getVerticaResourceFile() {
        Resource resource = new ClassPathResource("vertica.properties");
        return resource;
    }

    private Resource getDatabasePropertiesFile() {
        Resource resource = new ClassPathResource("mysql.properties");
        return resource;
    }
}

MyController.java

/*
 * MyController.java
 */
package com.test.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

/**
 *
 * @author
 */
@Component
public class MyController {

    @Autowired
    private MySqlProperties mySqlProperties;
    @Autowired
    private VerticaProperties verticaProperties;
    @Autowired
    private OtherProperties otherProperties;

    public String log() {
        System.out.println(mySqlProperties.getUsername());
        System.out.println(verticaProperties.getUsername());
        System.out.println(otherProperties.getKey());
        return "hello";
    }
}

MySqlProperties.java

/*
 * MySqlProperties.java
 */
package com.test.demo;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

/**
 *
 * @author
 */
@Component
public class MySqlProperties {

    @Value("${mysql-username}")
    private String username;
    @Value("${mysql-password}")
    private String password;

    //getter
}

VerticaProperties.java

/*
 * VerticaProperties.java
 */
package com.test.demo;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

/**
 *
 * @author
 */
@Component
public class VerticaProperties {

    @Value("${vertica-username}")
    private String username;
    @Value("${vertica-password}")
    private String password;

    //getter
}

OtherProperties.java

/*
 * OtherProperties.java
 */
package com.test.demo;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

/**
 *
 * @author
 */
@Component
public class OtherProperties {

    @Value("${key}")
    private String key;
    @Value("${key1}")
    private String key1;

    //getter
}

这些是属性文件。

mysql.properties

username=mysql
password=mysql

vertica.properties

username=vertica
password=vertica

other.properties

key=value
key1=value1

奇怪的问题：：当我从DemoApplication.java中删除以下代码时，该应用程序可以正常工作。

@Bean
    public PropertyPlaceholderConfigurer otherProps() {
        final PropertyPlaceholderConfigurer ppc = new PropertyPlaceholderConfigurer();
        ppc.setIgnoreResourceNotFound(true);

        final List<Resource> resourceList = new ArrayList<>();

        resourceList.add(getOtherResourceFile());

        ppc.setLocations(resourceList.toArray(new Resource[]{}));

        return ppc;
    }