Spring Boot official documentation chapter: Loading the application.properties configuration file
External, in the directory where the application runs
Built-in, in the resources/config package
Built-in, in the classpath root directory (under the resources directory)
Source code analysis
public class ConfigFileApplicationListener
implements EnvironmentPostProcessor, SmartApplicationListener, Ordered {
//...
//default configuration file name
private static final String DEFAULT_NAMES = "application";
// Note the order is from least to most specific (last one wins)
private static final String DEFAULT_SEARCH_LOCATIONS = "classpath:/,classpath:/config/,file:./,file:./config/";
public static final String CONFIG_LOCATION_PROPERTY = "spring.config.location";
public static final String CONFIG_NAME_PROPERTY = "spring.config.name";
//...
}
public void load() {
this.propertiesLoader = new PropertySourcesLoader();
this.activatedProfiles = false;
this.profiles = Collections.asLifoQueue(new LinkedList<Profile>());
this.processedProfiles = new LinkedList<Profile>();
//As mentioned in the previous section, the environment activated by the current profiles will be obtained, the default is default
Set<Profile> initialActiveProfiles = initializeActiveProfiles();
this.profiles.addAll(getUnprocessedActiveProfiles(initialActiveProfiles));
if (this.profiles.isEmpty()) {
for (String defaultProfileName : this.environment.getDefaultProfiles()) {
Profile defaultProfile = new Profile(defaultProfileName, true);
if (!this.profiles.contains(defaultProfile)) {
this.profiles.add(defaultProfile);
}
}
}
this.profiles.add(null);
while (!this.profiles.isEmpty()) {
Profile profile = this.profiles.poll();
//Get the search path of the configuration file
for (String location : getSearchLocations()) {
if (!location.endsWith("/")) {
// location is a filename already, so don't search for more
// filenames
load(location, null, profile);
}
else {
for (String name : getSearchNames()) {
load(location, name, profile);
}
}
}
this.processedProfiles.add(profile);
}
addConfigurationProperties(this.propertiesLoader.getPropertySources());
}
private Set<String> getSearchLocations() {
Set<String> locations = new LinkedHashSet<String>();
//User-defined configuration file, loaded first, specified by spring.config.location
if (this.environment.containsProperty(CONFIG_LOCATION_PROPERTY)) {
for (String path : asResolvedSet(
this.environment.getProperty(CONFIG_LOCATION_PROPERTY), null)) {
if (!path.contains("$")) {
path = StringUtils.cleanPath(path);
if (!ResourceUtils.isUrl(path)) {
path = ResourceUtils.FILE_URL_PREFIX + path;
}
}
locations.add(path);
}
}
//get search path
locations.addAll(
asResolvedSet(ConfigFileApplicationListener.this.searchLocations,
DEFAULT_SEARCH_LOCATIONS));
return locations;
}
private Set<String> asResolvedSet(String value, String fallback) {
List<String> list = Arrays.asList(StringUtils.trimArrayElements(
StringUtils.commaDelimitedListToStringArray(value != null
? this.environment.resolvePlaceholders(value) : fallback)));
//Reverse the elements, so the search path is actually the opposite of the order defined by DEFAULT_SEARCH_LOCATIONS.
Collections.reverse(list);
return new LinkedHashSet<String>(list);
}
private Set<String> getSearchNames() {
//If there is a configuration with spring.config.name in the environment, use this value as the configuration file name
if (this.environment.containsProperty(CONFIG_NAME_PROPERTY)) {
return asResolvedSet(this.environment.getProperty(CONFIG_NAME_PROPERTY),
null);
}
//Get the default configuration file name, the default is application
return asResolvedSet(ConfigFileApplicationListener.this.names, DEFAULT_NAMES);
}
public Set<String> getAllFileExtensions() {
Set<String> fileExtensions = new LinkedHashSet<String>();
//Get the suffix names of all configuration files, which are properties, xml, yml, yaml
for (PropertySourceLoader loader : this.loaders) {
fileExtensions.addAll(Arrays.asList(loader.getFileExtensions()));
}
return fileExtensions;
}
properties
xml
marl
yaml
And xml is used less, yml and yaml are actually the same format, so properties and yml are commonly used.
PropertySourcesLoader.doLoadIntoGroup()
private PropertySource<?> doLoadIntoGroup(String identifier, String location,
Profile profile) throws IOException {
Resource resource = this.resourceLoader.getResource(location);
PropertySource<?> propertySource = null;
StringBuilder msg = new StringBuilder();
if (resource != null && resource.exists()) {
String name = "applicationConfig: [" + location + "]";
String group = "applicationConfig: [" + identifier + "]";
propertySource = this.propertiesLoader.load(resource, group, name,
(profile == null ? null : profile.getName()));
if (propertySource != null) {
msg.append("Loaded ");
handleProfileProperties(propertySource);
}
else {
msg.append("Skipped (empty) ");
}
}
else {
msg.append("Skipped ");
}
msg.append("config file ");
msg.append(getResourceDescription(location, resource));
if (profile != null) {
msg.append(" for profile ").append(profile);
}
if (resource == null || !resource.exists()) {
msg.append(" resource not found");
this.logger.trace(msg);
}
else {
this.logger.debug(msg);
}
return propertySource;
}
Summarize
Read the configuration files with the suffixes of properties, xml, yml, yaml from the four locations: file:./config/, file:./, classpath:/config/, classpath:/
The priority is from high to low. For the same attribute configuration, the high-priority configuration will override the low-priority configuration; for other different attribute configurations, they will complement each other.
In the case of the same priority, there are application.properties and application.yml at the same time, then the properties in application.properties will override the properties in application.yml, because properties are loaded before yml.
When viewing the source code, in the getSearchLocations() code, you are prompted to change the default configuration file location through spring.config.location : After the project is packaged, use the command line parameter --spring.config.location=… To start the project, it is used to specify the new location of the configuration file, so that the specified new configuration file and the default loaded configuration file in the package work together to complement the configuration.
1java -jar spring-boot-02-config-SNAPSHOT.jar --spring.config.location=FBefore writing this blog post, the blogger encountered an unsolvable problem, see the link: Spring Boot loading configuration file priority problem ?
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