SpringBoot学习笔记3-EnvironmentPostProcessor

实现EnvironmentPostProcessor接口的类，可以做到：自定义启动配置项，允许上下文加载前定制化环境变量

1. 直接看EnvironmentPostProcessor类代码

package org.springframework.boot.env;

import org.apache.commons.logging.Log;

import org.springframework.boot.BootstrapContext;
import org.springframework.boot.BootstrapRegistry;
import org.springframework.boot.ConfigurableBootstrapContext;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.logging.DeferredLogFactory;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.Environment;

/**
 * 注释翻译后：
 * 允许上下文加载前定制化环境变量
 * 实现EnvironmentPostProcessor的接口，必须在文件 META-INF/spring.factories中注册。
 * 即，若不存在文件夹路径META-INF，则在resource下面创建该文件夹，并增加文件spring.factories。
 * 注册时使用类的全路径名作为key
 * 如果希望“调用有序”，则可以实现Ordered接口或@Ordered注解
 */
@FunctionalInterface
public interface EnvironmentPostProcessor {

	/**
	 * Post-process the given {@code environment}.
	 * @param environment the environment to post-process
	 * @param application the application to which the environment belongs
	 */
	void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application);

}

2. 定义一个类，实现EnvironmentPostProcessor接口

package com.example.other;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.env.EnvironmentPostProcessor;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.PropertiesPropertySource;
import org.springframework.core.env.PropertySource;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

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

/**
 自定义环境处理，在运行SpringApplication之前加载任意配置文件到Environment环境中
 */
public class MyEnvironmentPostProcessor implements EnvironmentPostProcessor {

    //Properties对象
    private final Properties properties = new Properties();

    @Override
    public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
        //自定义配置文件
        String[] profiles = {
                "swagger.properties"
//                "zzz.yml"
        };

        //循环添加
        for (String profile : profiles) {
            //从classpath路径下面查找文件
            Resource resource = new ClassPathResource(profile);
            //加载成PropertySource对象，并添加到Environment环境中
            environment.getPropertySources().addLast(loadProfiles(resource));
        }
    }

    //加载单个配置文件
    private PropertySource<?> loadProfiles(Resource resource) {
        if (!resource.exists()) {
            throw new IllegalArgumentException("资源" + resource + "不存在");
        }
        try {
            //从输入流中加载一个Properties对象
            properties.load(resource.getInputStream());
            return new PropertiesPropertySource(resource.getFilename(), properties);
        }catch (IOException ex) {
            throw new IllegalStateException("加载配置文件失败" + resource, ex);
        }
    }
}

3. 在resources 下添加META-INF文件夹

META-INF文件夹下加上 spring.factories文件，
spring.factories文件中配置org.springframework.boot.env.EnvironmentPostProcessor

#启用我们的自定义环境处理类
org.springframework.boot.env.EnvironmentPostProcessor=com.example.other.MyEnvironmentPostProcessor