Spring Environment源码解析

Environment关系图

从上图可以看出来 Environment 主要有三个实现类：

• MockEnvironment

  用于mock的

• StandardEnvironment

  标准的环境

• StandardServletEnvironment

  用于web的环境

分析一下常用的StandardEnvironment

public interface Environment extends PropertyResolver {

	//获取配置文件
	String[] getActiveProfiles();

    //获取默认的配置文件
	String[] getDefaultProfiles();
	
    //是否接受配置文件
	boolean acceptsProfiles(Profiles profiles);

}

//看一下接口 PropertyResolver
//PropertyResolver 主要是获取对应的Properties值，String或者进行数据类型转换后的值
//同时会处理占位符的数据
public interface PropertyResolver  {

	
	boolean containsProperty(String key);


	@Nullable
	String getProperty(String key);

	String getProperty(String key, String defaultValue);


	@Nullable
	<T> T getProperty(String key, Class<T> targetType);


	<T> T getProperty(String key, Class<T> targetType, T defaultValue);


	String getRequiredProperty(String key) throws IllegalStateException;


	<T> T getRequiredProperty(String key, Class<T> targetType) throws IllegalStateException;


	String resolvePlaceholders(String text);


	String resolveRequiredPlaceholders(String text) throws IllegalArgumentException;

}

看一下StandardEnvironment的代码

public class StandardEnvironment extends AbstractEnvironment {

	//系统的property名称
	public static final String SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME = "systemEnvironment";

	//JVM的property名称
	public static final String SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME = "systemProperties";


	//把系统的Properties和JVM的Properties存入
    //此方法在父类的构造函数中进行调用
	@Override
	protected void customizePropertySources(MutablePropertySources propertySources) {
		propertySources.addLast(new MapPropertySource(SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME, getSystemProperties()));
		propertySources.addLast(new SystemEnvironmentPropertySource(SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, getSystemEnvironment()));
	}

}