add a sample custom validator for AppProperties and add tests

spring-boot/configuration/src/main/java/io/reflectoring/validation/AppProperties.java

@@ -1,6 +1,8 @@
 package io.reflectoring.validation;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.validation.Errors;
+import org.springframework.validation.Validator;
 import org.springframework.validation.annotation.Validated;
 
 import javax.validation.Valid;
@@ -8,7 +10,7 @@ import javax.validation.constraints.NotBlank;
 
 @Validated
 @ConfigurationProperties(prefix = "app.properties")
-class AppProperties {
+class AppProperties implements Validator {
 
     @NotBlank
     private String name;
@@ -16,6 +18,23 @@ class AppProperties {
     @Valid
     private ReportProperties report;
 
+    private static final String APP_BASE_NAME = "Application";
+
+    public boolean supports(Class clazz) {
+        return AppProperties.class.isAssignableFrom(clazz);
+    }
+
+    public void validate(Object target, Errors errors) {
+
+        AppProperties appProperties = (AppProperties) target;
+        if (!appProperties.getName().endsWith(APP_BASE_NAME)) {
+            errors.rejectValue("name", "field.name.malformed",
+                    new Object[]{APP_BASE_NAME},
+                    "The application name must contain [" + APP_BASE_NAME + "] base name");
+        }
+
+    }
+
     public String getName() {
         return name;
     }

spring-boot/configuration/src/test/java/io/reflectoring/validation/PropertiesInvalidInputTest.java

@@ -37,7 +37,7 @@ class PropertiesInvalidInputTest {
     }
 
     @Test
-    void whenGivenNameEmpty_thenNotEmptyValidationFails() {
+    void whenGivenNameEmpty_thenNotBlankValidationFails() {
 
         properties.put("app.properties.name", "");
 
@@ -49,6 +49,19 @@ class PropertiesInvalidInputTest {
 
     }
 
+    @Test
+    void whenGivenNameDoesNotContainBaseName_thenCustomAppPropertiesValidatorFails() {
+
+        properties.put("app.properties.name", "My App");
+
+        assertThatThrownBy(application::run)
+                .isInstanceOf(ConfigurationPropertiesBindException.class)
+                .hasRootCauseInstanceOf(BindValidationException.class)
+                .hasStackTraceContaining("Field error in object 'app.properties' on field 'name'")
+                .hasStackTraceContaining("[The application name must contain [Application] base name]");
+
+    }
+
     @Test
     void whenGivenReportIntervalInDaysMoreThan30_thenMaxValidationFails() {
 
@@ -102,7 +115,7 @@ class PropertiesInvalidInputTest {
     }
 
     @Test
-    void whenGivenThirdPartyComponentNameIsEmpty_thenNotEmptyValidationFails() {
+    void whenGivenThirdPartyComponentNameIsEmpty_thenNotBlankValidationFails() {
 
         properties.put("app.third-party.properties.name", "");
 

spring-boot/configuration/src/test/java/io/reflectoring/validation/PropertiesValidInputTest.java

@@ -8,7 +8,7 @@ import org.springframework.boot.test.context.SpringBootTest;
 import static org.assertj.core.api.Assertions.assertThat;
 
 @SpringBootTest(properties = {
-        "app.properties.name=My Test App",
+        "app.properties.name=My Test Application",
         "app.properties.report.send-emails=true",
         "app.properties.report.type=PLAIN_TEXT",
         "app.properties.report.interval-in-days=14",
@@ -26,7 +26,7 @@ class PropertiesValidInputTest {
     @Test
     void appPropertiesAreLoaded() {
         assertThat(appProperties).isNotNull();
-        assertThat(appProperties.getName()).isEqualTo("My Test App");
+        assertThat(appProperties.getName()).isEqualTo("My Test Application");
         assertThat(appProperties.getReport()).isNotNull();
         assertThat(appProperties.getReport().getSendEmails()).isTrue();
         assertThat(appProperties.getReport().getType()).isEqualTo(ReportType.PLAIN_TEXT);