如何理解DubboDefaultProperties EnvironmentPostProcessor，相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。
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本文主要研究一下DubboDefaultPropertiesEnvironmentPostProcessor
DubboDefaultPropertiesEnvironmentPostProcessor
dubbo-spring-boot-project-2.7.3/dubbo-spring-boot-compatible/autoconfigure/src/main/java/org/apache/dubbo/spring/boot/env/DubboDefaultPropertiesEnvironmentPostProcessor.java
public class DubboDefaultPropertiesEnvironmentPostProcessor implements EnvironmentPostProcessor, Ordered {
/**
* The name of default {@link PropertySource} defined in SpringApplication#configurePropertySources method.
*/
public static final String PROPERTY_SOURCE_NAME = "defaultProperties";
/**
* The property name of "spring.main.allow-bean-definition-overriding".
* Please refer to: https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.1-Release-Notes#bean-overriding
*/
public static final String ALLOW_BEAN_DEFINITION_OVERRIDING_PROPERTY = "spring.main.allow-bean-definition-overriding";
@Override
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
MutablePropertySources propertySources = environment.getPropertySources();
Map defaultProperties = createDefaultProperties(environment);
if (!CollectionUtils.isEmpty(defaultProperties)) {
addOrReplace(propertySources, defaultProperties);
}
}
@Override
public int getOrder() {
return LOWEST_PRECEDENCE;
}
private Map createDefaultProperties(ConfigurableEnvironment environment) {
Map defaultProperties = new HashMap();
setDubboApplicationNameProperty(environment, defaultProperties);
setDubboConfigMultipleProperty(defaultProperties);
setDubboApplicationQosEnableProperty(defaultProperties);
setAllowBeanDefinitionOverriding(defaultProperties);
return defaultProperties;
}
private void setDubboApplicationNameProperty(Environment environment, Map defaultProperties) {
String springApplicationName = environment.getProperty(SPRING_APPLICATION_NAME_PROPERTY);
if (StringUtils.hasLength(springApplicationName)
&& !environment.containsProperty(DUBBO_APPLICATION_NAME_PROPERTY)) {
defaultProperties.put(DUBBO_APPLICATION_NAME_PROPERTY, springApplicationName);
}
}
private void setDubboConfigMultipleProperty(Map defaultProperties) {
defaultProperties.put(DUBBO_CONFIG_MULTIPLE_PROPERTY, Boolean.TRUE.toString());
}
private void setDubboApplicationQosEnableProperty(Map defaultProperties) {
defaultProperties.put(DUBBO_APPLICATION_QOS_ENABLE_PROPERTY, Boolean.FALSE.toString());
}
/**
* Set {@link #ALLOW_BEAN_DEFINITION_OVERRIDING_PROPERTY "spring.main.allow-bean-definition-overriding"} to be
* true as default.
*
* @param defaultProperties the default {@link Properties properties}
* @see #ALLOW_BEAN_DEFINITION_OVERRIDING_PROPERTY
* @since 2.7.1
*/
private void setAllowBeanDefinitionOverriding(Map defaultProperties) {
defaultProperties.put(ALLOW_BEAN_DEFINITION_OVERRIDING_PROPERTY, Boolean.TRUE.toString());
}
/**
* Copy from BusEnvironmentPostProcessor#addOrReplace(MutablePropertySources, Map)
*
* @param propertySources {@link MutablePropertySources}
* @param map Default Dubbo Properties
*/
private void addOrReplace(MutablePropertySources propertySources,
Map map) {
MapPropertySource target = null;
if (propertySources.contains(PROPERTY_SOURCE_NAME)) {
PropertySource source = propertySources.get(PROPERTY_SOURCE_NAME);
if (source instanceof MapPropertySource) {
target = (MapPropertySource) source;
for (String key : map.keySet()) {
if (!target.containsProperty(key)) {
target.getSource().put(key, map.get(key));
}
}
}
}
if (target == null) {
target = new MapPropertySource(PROPERTY_SOURCE_NAME, map);
}
if (!propertySources.contains(PROPERTY_SOURCE_NAME)) {
propertySources.addLast(target);
}
}
}DubboDefaultPropertiesEnvironmentPostProcessor实现了EnvironmentPostProcessor, Ordered接口；postProcessEnvironment方法首先从environment获取MutablePropertySources，然后通过createDefaultProperties创建默认配置defaultProperties(这里默认设置了DUBBO_APPLICATION_NAME_PROPERTY为springApplicationName、DUBBO_CONFIG_MULTIPLE_PROPERTY为true、DUBBO_APPLICATION_QOS_ENABLE_PROPERTY为false)，最后通过addOrReplace方法把defaultProperties覆盖到propertySources；getOrder方法返回的是LOWEST_PRECEDENCE
DubboDefaultPropertiesEnvironmentPostProcessorTest
dubbo-spring-boot-project-2.7.3/dubbo-spring-boot-autoconfigure/src/test/java/org/apache/dubbo/spring/boot/env/DubboDefaultPropertiesEnvironmentPostProcessorTest.java
public class DubboDefaultPropertiesEnvironmentPostProcessorTest {
private DubboDefaultPropertiesEnvironmentPostProcessor instance =
new DubboDefaultPropertiesEnvironmentPostProcessor();
private SpringApplication springApplication = new SpringApplication();
@Test
public void testOrder() {
Assert.assertEquals(Ordered.LOWEST_PRECEDENCE, instance.getOrder());
}
@Test
public void testPostProcessEnvironment() {
MockEnvironment environment = new MockEnvironment();
// Case 1 : Not Any property
instance.postProcessEnvironment(environment, springApplication);
// Get PropertySources
MutablePropertySources propertySources = environment.getPropertySources();
// Nothing to change
PropertySource defaultPropertySource = propertySources.get("defaultProperties");
Assert.assertNotNull(defaultPropertySource);
Assert.assertEquals("true", defaultPropertySource.getProperty("dubbo.config.multiple"));
Assert.assertEquals("false", defaultPropertySource.getProperty("dubbo.application.qos-enable"));
// Case 2 : Only set property "spring.application.name"
environment.setProperty("spring.application.name", "demo-dubbo-application");
instance.postProcessEnvironment(environment, springApplication);
defaultPropertySource = propertySources.get("defaultProperties");
Object dubboApplicationName = defaultPropertySource.getProperty("dubbo.application.name");
Assert.assertEquals("demo-dubbo-application", dubboApplicationName);
// Case 3 : Only set property "dubbo.application.name"
// Rest environment
environment = new MockEnvironment();
propertySources = environment.getPropertySources();
environment.setProperty("dubbo.application.name", "demo-dubbo-application");
instance.postProcessEnvironment(environment, springApplication);
defaultPropertySource = propertySources.get("defaultProperties");
Assert.assertNotNull(defaultPropertySource);
dubboApplicationName = environment.getProperty("dubbo.application.name");
Assert.assertEquals("demo-dubbo-application", dubboApplicationName);
// Case 4 : If "defaultProperties" PropertySource is present in PropertySources
// Rest environment
environment = new MockEnvironment();
propertySources = environment.getPropertySources();
propertySources.addLast(new MapPropertySource("defaultProperties", new HashMap()));
environment.setProperty("spring.application.name", "demo-dubbo-application");
instance.postProcessEnvironment(environment, springApplication);
defaultPropertySource = propertySources.get("defaultProperties");
dubboApplicationName = defaultPropertySource.getProperty("dubbo.application.name");
Assert.assertEquals("demo-dubbo-application", dubboApplicationName);
// Case 5 : Rest dubbo.config.multiple and dubbo.application.qos-enable
environment = new MockEnvironment();
propertySources = environment.getPropertySources();
propertySources.addLast(new MapPropertySource("defaultProperties", new HashMap()));
environment.setProperty("dubbo.config.multiple", "false");
environment.setProperty("dubbo.application.qos-enable", "true");
instance.postProcessEnvironment(environment, springApplication);
Assert.assertEquals("false", environment.getProperty("dubbo.config.multiple"));
Assert.assertEquals("true", environment.getProperty("dubbo.application.qos-enable"));
}
}小结
DubboDefaultPropertiesEnvironmentPostProcessor实现了EnvironmentPostProcessor, Ordered接口；postProcessEnvironment方法首先从environment获取MutablePropertySources，然后通过createDefaultProperties创建默认配置defaultProperties(这里默认设置了DUBBO_APPLICATION_NAME_PROPERTY为springApplicationName、DUBBO_CONFIG_MULTIPLE_PROPERTY为true、DUBBO_APPLICATION_QOS_ENABLE_PROPERTY为false)，最后通过addOrReplace方法把defaultProperties覆盖到propertySources；getOrder方法返回的是LOWEST_PRECEDENCE
doc
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