、

nacos， nacos ， 。 ？

You can modify it when you start the NACOS configuration at the local SpringBoot project.

2. Take an example

For example:The server.tomcat.basedir configuration configured in NACOS (Tomcat Temporary Directory) is unable to create the corresponding folder in my local area, which makes it impossible to start the item, so I can only modify the value of the server.tomcat.basedir (it cannot be modified yet. Nacos cloud configuration).

Unable to create the corresponding directory, as shown in the figure:

The project starts an error, as shown in the figure:

 

3. Solution

The first method is to modify the breakpoint debugging function of IDEA

1. We find the Loadnacosdata method of NacospRopertysourceBuilder class, and hit the breakpoint to as shown in the figure as shown in the figure

2. Use Evaluate to execute the DataMAP.Put () method to overwrite the value.

The above operations are only suitable for temporary startups. Each time it starts, it must be modified, which is very troublesome. You can use the second method.

The second method is to modify the code with code

1. First customize a class to implement SpringApplicationRunListener interface.

SpringApplicationRunListener is the life cycle of SpringBoot. If you don’t understand, please refer to:SpringBoot expansion point

@Slf4j
public class LocalHostSpringApplicationRunListener implements SpringApplicationRunListener {

    /**
     * Must be added to SpringApplication Application and String [] ARGS constructor, otherwise start an error
     * @param application
     * @param args
     */
    public LocalHostSpringApplicationRunListener(SpringApplication application, String[] args) {
    }

    @Override
    public void starting() {
    }

    @Override
    public void environmentPrepared(ConfigurableEnvironment environment) {
    }

    /**
           * When the context is ready to be completed
     * @param context the application context
     */
    @Override
    public void contextPrepared(ConfigurableApplicationContext context) {
                 // Judging the context environment is the service environment
        if(context instanceof AnnotationConfigServletWebServerApplicationContext){
                         // Get the total configuration information from the context environment
            MutablePropertySources mutablePropertySources = context.getEnvironment().getPropertySources();
                         // Get NACOS configuration information
            CompositePropertySource bootstrapPropertiesCompositePropertySource = (CompositePropertySource)mutablePropertySources.get("bootstrapProperties");
                         // Get the configuration information in NACOS configuration information (several layers of packaging)
            for (PropertySource compositePropertySource : bootstrapPropertiesCompositePropertySource.getPropertySources()) {
                for (PropertySource nacosPropertySource : ((CompositePropertySource) compositePropertySource).getPropertySources()) {
                                         // Finally get the corresponding configuration file information
                    NacosPropertySource nacosPropertySourceTarget = (NacosPropertySource) nacosPropertySource;
                                         // Find the file name you want to modify (Dataid)
                    if("sys-test.properties".equals(nacosPropertySourceTarget.getDataId())){
                                                 // Modify the value
                        Map<String, Object> source = nacosPropertySourceTarget.getSource();
                        source.put("server.tomcat.basedir","/tmp");
                                                 Log.info ("The modified server.tomcat.basedir is/tmp");
                    }
                };
            };
        }
    }

    @Override
    public void contextLoaded(ConfigurableApplicationContext context) {
    }

    @Override
    public void started(ConfigurableApplicationContext context) {

    }

    @Override
    public void running(ConfigurableApplicationContext context) {

    }

    @Override
    public void failed(ConfigurableApplicationContext context, Throwable exception) {

    }
}

2. Create a spring.factories file in the meta-inf folder under the Resources folder

Explanation: Spring Factories is a decoupled expansion mechanism of Spring Boot. It imitates the expansion mechanism of the SPI in Java and can realize Bean other than scanned packets.

 

3、

：

1、 ，nacos springboot “ ”。
spingboot prepareContext ， applyInitializers 。

PropertySourceBootstrapConfiguration springcloud 。

From the code we can see Listeners.ContextPrepared (Context); so we can just use the "context preparation phase" of the SpringBoot life cycle to modify NACOS configuration.

2、 SpringApplicationRunListener springboot

ConfigurableApplicationContext ， Environment 。

Environment PropertySources 。

Because there are multiple configuration information (local configuration, NACOS configuration, etc.), we have to find the configuration information of NACOS, get MAP layer by layer and then modify