Spring Boot：@PropertySource读取指定配置文件与解决不兼容YAML文件问题

测试代码

​​pom.xml​​：

<?xml version="1.0" encoding="UTF-8"?>
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.2</version>
    </parent>

    <packaging>jar</packaging>

    <groupId>com.kaven</groupId>
    <artifactId>springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <name>springboot</name>
    <description>springboot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

​​user.properties​​：

user.username=kaven
user.password=itkaven
user.hobbies[0]=打乒乓球
user.hobbies[1]=跑步
user.hobbies[2]=比赛
user.scores.mathematics=150
user.scores.english=100
user.user-token[0].token=jdsnjvd430=bkjgfnmbj
user.user-token[1].token=4imkmklf034mflkmfg-3=
user.user-token[2].token=mgklfmj498mnmgjnmfnjj

​​UserToken​​​类（用户​​Token​​）：

package com.kaven.springboot.config;

import lombok.Setter;
import lombok.ToString;

@Setter
@ToString
public class UserToken {
    private String token;
}

​​UserProperties​​类（用户参数）：

package com.kaven.springboot.config;

import lombok.Setter;
import lombok.ToString;
import org.springframework.boot.context.properties.ConfigurationProperties;

import java.util.List;
import java.util.Map;
import java.util.Set;

@ConfigurationProperties(prefix = "user")
@ToString
@Setter
public class UserProperties {
    private String username;
    private String password;
    private Set<String> hobbies;
    private Map<String, Integer> scores;
    private List<UserToken> userToken;
}

​​UserConfig​​类（用于读取指定配置文件）：

package com.kaven.springboot.config;

import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
@PropertySource(value = "classpath:/static/user.properties")
public class UserConfig {

}

接口（获取用户参数）：

package com.kaven.springboot.controller;

import com.google.gson.Gson;
import com.kaven.springboot.config.UserProperties;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

@RestController
public class ConfigController {

    private static final Gson GSON = new Gson();

    @Resource
    private UserProperties userProperties;

    @GetMapping("/config")
    public String getConfig() {
        String result = GSON.toJson(userProperties);
        System.out.println(result);
        return result;
    }
}

启动类：

package com.kaven.springboot;

import com.kaven.springboot.config.UserProperties;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.ConfigurationPropertiesScan;

@SpringBootApplication
@ConfigurationPropertiesScan(basePackageClasses = {UserProperties.class})
public class SpringbootApplication {
    public static void main(String[] args) {
        SpringApplication application = new SpringApplication(SpringbootApplication.class);
        application.run(args);
    }
}

启动应用，使用​​Postman​​请求接口，响应符合预期。

很显然使用​​@PropertySource​​​注解读取到了指定配置文件，并通过​​@ConfigurationProperties​​​注解将配置文件中的配置项绑定到了​​UserProperties​​实例。

忽略未找到资源

当未找到​​@PropertySource​​注解指定的资源时，启动应用会报错。

package com.kaven.springboot.config;

import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
@PropertySource(value = "classpath:/static/1.properties")
public class UserConfig {

}

如果该资源文件完全是可选的，则​​@PropertySource​​​注解的​​ignoreResourceNotFound​​​属性设置为​​true​​是合适的。

package com.kaven.springboot.config;

import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
@PropertySource(value = "classpath:/static/1.properties", ignoreResourceNotFound = true)
public class UserConfig {

}

应用可以正常启动。

只是接口的响应是空的。

设置编码

通过设置​​@PropertySource​​​注解的​​encoding​​属性来设置编码，即指定资源的特定字符编码。

package com.kaven.springboot.config;

import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
@PropertySource(value = "classpath:/static/1.properties", ignoreResourceNotFound = true, encoding = "UTF-8")
public class UserConfig {

}

读取YAML文件存在问题

将配置文件修改成​​YAML​​文件格式。

user:
  username: kaven
  password: itkaven
  hobbies:
    - "打乒乓球"
    - "跑步"
    - "比赛"
  scores:
    mathematics: 150
    english: 100
  user-token:
    - token: jdsnjvd430=bkjgfnmbj
    - token: 4imkmklf034mflkmfg-3=
    - token: mgklfmj498mnmgjnmfnjj

修改​​UserConfig​​：

package com.kaven.springboot.config;

import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
@PropertySource(value = "classpath:/static/user.yml", ignoreResourceNotFound = true, encoding = "UTF-8")
public class UserConfig {

}

启动应用，请求接口，此时响应为空。

​​Spring​​​只提供了一个默认的​​PropertySourceFactory​​​，即​​DefaultPropertySourceFactory​​类。

package org.springframework.core.io.support;

import java.io.IOException;
import org.springframework.core.env.PropertySource;
import org.springframework.lang.Nullable;

public class DefaultPropertySourceFactory implements PropertySourceFactory {
    public DefaultPropertySourceFactory() {
    }

    public PropertySource<?> createPropertySource(@Nullable String name, EncodedResource resource) throws IOException {
        return name != null ? new ResourcePropertySource(name, resource) : new ResourcePropertySource(resource);
    }
}

不难发现这个工厂是用​​PropertiesLoaderUtils.loadProperties(resource)​​来加载属性文件。

public ResourcePropertySource(String name, EncodedResource resource) throws IOException {
        super(name, PropertiesLoaderUtils.loadProperties(resource));
        this.resourceName = getNameForResource(resource.getResource());
    }

    public ResourcePropertySource(EncodedResource resource) throws IOException {
        super(getNameForResource(resource.getResource()), PropertiesLoaderUtils.loadProperties(resource));
        this.resourceName = null;
    }

继续看源码可以发现​​Spring​​​提供的​​@PropertySource​​​注解并没有兼容​​YAML​​​文件的解析。​​@PropertySource​​​注解中，有一个​​factory​​​属性，可指定一个自定义的​​PropertySourceFactory​​​接口实现，用于解析指定的文件。默认的实现是​​DefaultPropertySourceFactory​​​类，使用​​Properties​​进行解析。

自定义PropertySourceFactory兼容YAML文件

​​CompositePropertySourceFactory​​​类（继承​​DefaultPropertySourceFactory​​类）：

package com.kaven.springboot.config;

import org.springframework.beans.factory.config.YamlPropertiesFactoryBean;
import org.springframework.core.env.PropertiesPropertySource;
import org.springframework.core.env.PropertySource;
import org.springframework.core.io.support.DefaultPropertySourceFactory;
import org.springframework.core.io.support.EncodedResource;

import java.io.IOException;
import java.util.Optional;
import java.util.Properties;

public class CompositePropertySourceFactory extends DefaultPropertySourceFactory {
    @Override
    public PropertySource<?> createPropertySource(String name, EncodedResource resource)
            throws IOException {
        String sourceName = Optional.ofNullable(name).orElse(resource.getResource().getFilename());

        // sourceName不能为空
        assert sourceName != null;

        // 源文件不存在
        if (!resource.getResource().exists()) {
            // 返回一个空的属性
            return new PropertiesPropertySource(sourceName, new Properties());
        }
        // 源文件存在
        else {
            // yaml文件格式解析
            if (sourceName.endsWith(".yml") || sourceName.endsWith(".yaml")) {
                Properties propertiesFromYaml = loadYaml(resource);
                return new PropertiesPropertySource(sourceName, propertiesFromYaml);
            }
            // 其他文件格式解析
            // 委托给父类
            else {
                return super.createPropertySource(name, resource);
            }
        }
    }

    private Properties loadYaml(EncodedResource resource) throws IOException {
        YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
        factory.setResources(resource.getResource());
        factory.afterPropertiesSet();
        return factory.getObject();
    }
}

修改​​UserConfig​​：

package com.kaven.springboot.config;

import org.springframework.context.annotation.PropertySource;
import org.springframework.stereotype.Component;

@Component
@PropertySource(value = "classpath:/static/user.yml", ignoreResourceNotFound = true, encoding = "UTF-8", factory = CompositePropertySourceFactory.class)
public class UserConfig {

}

启动应用，请求接口，响应符合预期。

再将配置文件修改成​​Properties​​文件格式进行测试，响应符合预期。

​​@PropertySource​​​读取指定配置文件与解决不兼容​​YAML​​文件问题就介绍到这里，如果博主有说错的地方或者大家有不同的见解，欢迎大家评论补充。