Three new article modules: configuration binding, profiles and config data, Spring AOP
configuration-properties/ @ConfigurationProperties vs @Value on Spring Boot 4.1.1. The relaxed-binding matrix is generated by binding each spelling rather than transcribed, and re-checked against real processes -- the in-process probe was wrong twice before it was right. Records the three findings that came out of it: @Value does get relaxed resolution inside Spring Boot (Boot attaches ConfigurationPropertySources), the configuration processor silently stops generating metadata on JDK 23+ when declared as a plain dependency, and @Valid is not what makes nested constraints run. profiles-and-config/ Precedence, profiles, spring.config.import and config trees. /precedence reports every source holding a property in rank order with file and line, which turns "my profile file had no effect" into a two-line answer. Also pins the counterintuitive one: an imported file outranks the file that imported it. spring-aop/ Designators, proxy types, and aspects that do not fire. One advice per supported designator so the reference table is generated from real matches; all fourteen unsupported designators fed to the parser. Two corrections to the reference documentation: unsupported designators throw UnsupportedPointcutPrimitiveException (extends RuntimeException, not IllegalArgumentException), and spring-boot-starter-aop was renamed to spring-boot-starter-aspectj in Boot 4. 19 contract tests across the three modules, 15 captured transcripts, all regenerated by scripts/run-all.sh. Verified on Spring Boot 4.1.1, Spring Framework 7.0.9, JDK 25.0.4.1. Co-Authored-By: Claude Opus 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01Gip4srpzMwjgoba6uEfbr5
This commit is contained in:
Claude Opus 5
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package com.ankurm.profiles;
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import org.springframework.boot.SpringApplication;
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import org.springframework.boot.autoconfigure.SpringBootApplication;
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/**
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* Companion application for the ankurm.com article
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* "Spring Boot Profiles Done Right: Config Import, Config Trees and Kubernetes ConfigMaps".
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*
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* <p>Every scenario in {@code scripts/} starts this same application with a different
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* combination of profiles, imported locations and environment variables, and asks it one
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* question: which source won, and which sources were present and lost.
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*/
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@SpringBootApplication
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public class ProfilesApplication {
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public static void main(String[] args) {
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SpringApplication.run(ProfilesApplication.class, args);
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}
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}
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package com.ankurm.profiles.web;
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import java.util.ArrayList;
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import java.util.LinkedHashMap;
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import java.util.List;
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import java.util.Map;
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import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
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import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
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import org.springframework.boot.context.properties.source.ConfigurationPropertySources;
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import org.springframework.core.env.ConfigurableEnvironment;
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import org.springframework.core.env.EnumerablePropertySource;
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import org.springframework.core.env.PropertySource;
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import org.springframework.web.bind.annotation.GetMapping;
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import org.springframework.web.bind.annotation.RequestParam;
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import org.springframework.web.bind.annotation.RestController;
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/**
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* The endpoint the whole article is built on: for one property, every source that holds a
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* value for it, in precedence order, with the winner first.
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*
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* <p>"I set it in {@code application-prod.yaml} and it had no effect" is not a mystery once
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* you can see that four sources hold the property and yours is third. Spring Boot knows the
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* answer; it just never volunteers it.
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*
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* <p>Documented in {@code docs/03-seeing-precedence.md}. Delete it before shipping: it will
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* print whatever a mounted secret contains.
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*/
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@RestController
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public class PrecedenceEndpoint {
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private final ConfigurableEnvironment environment;
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public PrecedenceEndpoint(ConfigurableEnvironment environment) {
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this.environment = environment;
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}
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/** Every source holding {@code name}, highest precedence first. */
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@GetMapping("/precedence")
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public Map<String, Object> precedence(
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@RequestParam(defaultValue = "demo.greeting") String name) {
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ConfigurationPropertyName propertyName = ConfigurationPropertyName.of(name);
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List<Map<String, Object>> holders = new ArrayList<>();
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for (ConfigurationPropertySource source : ConfigurationPropertySources.get(environment)) {
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var property = source.getConfigurationProperty(propertyName);
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if (property == null) {
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continue;
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}
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Map<String, Object> row = new LinkedHashMap<>();
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row.put("rank", holders.size() + 1);
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row.put("source", shortName(source.getUnderlyingSource()));
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row.put("value", String.valueOf(property.getValue()));
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row.put("origin", String.valueOf(property.getOrigin()));
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holders.add(row);
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}
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Map<String, Object> result = new LinkedHashMap<>();
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result.put("property", name);
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result.put("effectiveValue", environment.getProperty(name));
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result.put("activeProfiles", List.of(environment.getActiveProfiles()));
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result.put("holders", holders);
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result.put("shadowedCount", Math.max(0, holders.size() - 1));
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return result;
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}
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/** The environment's property sources in order, so the article can show the real stack. */
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@GetMapping("/sources")
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public List<Map<String, Object>> sources() {
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List<Map<String, Object>> rows = new ArrayList<>();
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int rank = 1;
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for (PropertySource<?> source : environment.getPropertySources()) {
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Map<String, Object> row = new LinkedHashMap<>();
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row.put("rank", rank++);
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row.put("name", source.getName());
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row.put("type", source.getClass().getSimpleName());
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if (source instanceof EnumerablePropertySource<?> enumerable) {
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row.put("propertyCount", enumerable.getPropertyNames().length);
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}
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rows.add(row);
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}
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return rows;
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}
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private String shortName(Object underlying) {
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String text = String.valueOf(underlying);
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return text.length() > 150 ? text.substring(0, 150) + "..." : text;
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}
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}
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# spring.profiles.active cannot be set from a document that is itself profile-specific.
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# Spring Boot refuses this rather than silently half-applying it. The exact exception is
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# captured in docs/output/05-invalid-activation.txt.
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demo:
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greeting: from-badactivation
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---
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spring:
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config:
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activate:
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on-profile: staging
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profiles:
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active: sneaky
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# Demonstrates spring.config.import ordering.
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#
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# The imported document is processed as though it appeared immediately AFTER this one, which
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# means the importing file wins on any key both of them set. That is the opposite of the
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# intuition most people bring from #include, and it is the subject of docs/05-config-import.md.
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spring:
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config:
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import: "optional:classpath:/imported.yaml"
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demo:
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greeting: from-application-import-yaml
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# One file, three documents, activated by condition rather than by filename.
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#
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# spring.config.activate.on-profile is the mechanism behind profile-specific behaviour when
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# you would rather keep everything in one file. Later documents win over earlier ones.
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demo:
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greeting: from-multidoc-default-document
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---
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spring:
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config:
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activate:
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on-profile: staging
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demo:
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greeting: from-multidoc-staging-document
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---
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spring:
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config:
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activate:
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on-profile: prod
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demo:
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greeting: from-multidoc-prod-document
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# Activated as part of the "prod" profile group declared in application.yaml.
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demo:
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pool-size: 40
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# The second member of the "prod" group.
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demo:
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metrics-enabled: true
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# Profile-specific configuration. This file always beats application.yaml -- and still loses
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# to an environment variable, which is the point of docs/04-why-your-profile-file-lost.md.
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demo:
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greeting: from-application-prod-yaml
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datasource-url: jdbc:postgresql://prod-db:5432/orders
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spring:
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application:
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name: profiles-and-config
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profiles:
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# A profile group: activating "prod" activates all three. Groups are resolved before
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# config data is processed, which is why a group can be declared here and still affect
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# which application-<profile>.yaml files are loaded.
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group:
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prod: prod-db,prod-metrics
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server:
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port: 8080
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logging:
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level:
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root: WARN
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demo:
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# The property every scenario asks about. Each source below sets it to a string naming
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# itself, so the winner is self-identifying in the transcript.
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greeting: from-application-yaml
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datasource-url: jdbc:h2:mem:default
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# Imported by application-import.yaml. Sets the same key, and loses.
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demo:
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greeting: from-imported-yaml
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imported-only: yes-this-file-was-read
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package com.ankurm.profiles;
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import org.junit.jupiter.api.DisplayName;
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import org.junit.jupiter.api.Test;
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import org.springframework.boot.SpringApplication;
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import org.springframework.boot.WebApplicationType;
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import org.springframework.context.ConfigurableApplicationContext;
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import org.springframework.core.env.ConfigurableEnvironment;
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import static org.assertj.core.api.Assertions.assertThat;
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/**
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* Pins the precedence claims the article makes, so a future Spring Boot upgrade that changes
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* any of them fails the build rather than quietly making the article wrong.
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*/
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class PrecedenceContractTests {
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private ConfigurableApplicationContext run(String... args) {
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SpringApplication application = new SpringApplication(ProfilesApplication.class);
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application.setWebApplicationType(WebApplicationType.NONE);
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return application.run(args);
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}
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@Test
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@DisplayName("a profile-specific file beats application.yaml")
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void profileFileBeatsBaseFile() {
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try (var context = run("--spring.profiles.active=prod")) {
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assertThat(context.getEnvironment().getProperty("demo.greeting"))
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.isEqualTo("from-application-prod-yaml");
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}
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}
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@Test
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@DisplayName("a profile group activates every profile it names")
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void profileGroupExpands() {
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try (var context = run("--spring.profiles.active=prod")) {
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assertThat(context.getEnvironment().getActiveProfiles())
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.containsExactlyInAnyOrder("prod", "prod-db", "prod-metrics");
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assertThat(context.getEnvironment().getProperty("demo.pool-size")).isEqualTo("40");
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}
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}
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@Test
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@DisplayName("a command-line argument beats every config file")
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void commandLineBeatsConfigData() {
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try (var context = run("--spring.profiles.active=prod",
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"--demo.greeting=from-command-line")) {
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assertThat(context.getEnvironment().getProperty("demo.greeting"))
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.isEqualTo("from-command-line");
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}
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}
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/**
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* The counterintuitive one, and the reason the article has a callout about it: an
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* imported document outranks the document that imported it.
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*/
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@Test
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@DisplayName("spring.config.import: the IMPORTED file wins over the importing file")
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void importedFileWins() {
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try (var context = run("--spring.profiles.active=import")) {
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ConfigurableEnvironment environment = context.getEnvironment();
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assertThat(environment.getProperty("demo.imported-only"))
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.as("the import was processed at all")
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.isEqualTo("yes-this-file-was-read");
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assertThat(environment.getProperty("demo.greeting"))
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.as("and it beat application-import.yaml, which declared the import")
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.isEqualTo("from-imported-yaml");
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}
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}
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@Test
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@DisplayName("later documents in a multi-document file win over earlier ones")
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void multiDocumentOrdering() {
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try (var context = run("--spring.profiles.active=multidoc")) {
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assertThat(context.getEnvironment().getProperty("demo.greeting"))
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.isEqualTo("from-multidoc-default-document");
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}
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try (var context = run("--spring.profiles.active=multidoc,staging")) {
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assertThat(context.getEnvironment().getProperty("demo.greeting"))
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.isEqualTo("from-multidoc-staging-document");
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}
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}
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@Test
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@DisplayName("a config tree beats application.yaml but still loses to nothing above it")
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void configTreeIsConfigData(@org.junit.jupiter.api.io.TempDir java.nio.file.Path mount)
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throws Exception {
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java.nio.file.Files.writeString(mount.resolve("demo.greeting"), "from-config-tree");
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try (var context = run("--spring.config.import=configtree:" + mount + "/")) {
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assertThat(context.getEnvironment().getProperty("demo.greeting"))
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.isEqualTo("from-config-tree");
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}
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// A command-line argument still outranks it: a config tree is config data.
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try (var context = run("--spring.config.import=configtree:" + mount + "/",
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"--demo.greeting=from-command-line")) {
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assertThat(context.getEnvironment().getProperty("demo.greeting"))
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.isEqualTo("from-command-line");
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}
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}
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}
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