[kiworkshop#106] ad JwtConverter.

community-backend/build.gradle

@@ -20,6 +20,8 @@ ext {
 	// springCloudVersion = "Greenwich.RELEASE" // TODO: replace
 	springCloudVersion = "Greenwich.SR1"
 	springSecurityOAuth2AutoConfigureVersion = "2.1.9.RELEASE"
+
+	jwtVersion = '3.10.3'
 }
 
 task dockerComposeUp(type: Exec) {

community-backend/core/core-jwt-converter/build.gradle

@@ -0,0 +1,10 @@
+plugins {
+    id 'java-library'
+}
+
+dependencies {
+    api project(':module:module-object-mapper-async')
+
+    implementation 'org.springframework.boot:spring-boot-starter-webflux'
+    implementation "com.auth0:java-jwt:${jwtVersion}"
+}

community-backend/core/core-jwt-converter/src/main/java/org/kiworkshop/community/util/JwtConverter.java

@@ -0,0 +1,40 @@
+package org.kiworkshop.community.util;
+
+import com.auth0.jwt.JWT;
+import com.auth0.jwt.algorithms.Algorithm;
+import com.auth0.jwt.interfaces.JWTVerifier;
+import lombok.Builder;
+import org.springframework.util.Assert;
+import reactor.core.publisher.Mono;
+
+public class JwtConverter<T> {
+  private static final int JWT_SECRET_MIN_LENGTH = 32;
+
+  private final Class<T> clazz;
+  private final ObjectMapperAsync objectMapperAsync;
+
+  private final Algorithm algorithm;
+  private final JWTVerifier jwtVerifier;
+
+  @Builder
+  private JwtConverter(Class<T> clazz, String jwtSecret, ObjectMapperAsync objectMapperAsync) {
+    Assert.isTrue(jwtSecret.getBytes().length >= JWT_SECRET_MIN_LENGTH,
+        "jwtSecret's length must be large or equal than " + JWT_SECRET_MIN_LENGTH);
+
+    this.clazz = clazz;
+    this.objectMapperAsync = objectMapperAsync;
+    this.algorithm = Algorithm.HMAC256(jwtSecret);
+    this.jwtVerifier = JWT.require(this.algorithm).build();
+  }
+
+  public Mono<String> encode(T subject) {
+    return objectMapperAsync.writeValueAsString(subject)
+        .map(subjectAlter -> JWT.create().withSubject(subjectAlter).sign(algorithm));
+  }
+
+  public Mono<T> decode(String jwt) {
+    String serializedSubject = jwtVerifier.verify(jwt).getSubject();
+
+    return objectMapperAsync.readValue(serializedSubject, clazz);
+  }
+}

community-backend/core/core-jwt-converter/src/test/java/org/kiworkshop/community/util/JwtConverterTest.java

@@ -0,0 +1,64 @@
+package org.kiworkshop.community.util;
+
+import static org.assertj.core.api.BDDAssertions.then;
+import static org.assertj.core.api.BDDAssertions.thenThrownBy;
+
+import java.time.ZonedDateTime;
+import java.util.Objects;
+import lombok.Getter;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.http.codec.json.Jackson2JsonDecoder;
+import org.springframework.http.codec.json.Jackson2JsonEncoder;
+
+@ExtendWith(MockitoExtension.class)
+class JwtConverterTest {
+  private static final ZonedDateTime now = ZonedDateTime.now();
+  private static final String jwtSecret = "secretKeyEqualOrLargerThan32byte";
+
+  @Getter
+  static class Sample {
+    String field = "field";
+    ZonedDateTime zonedDateTime = now;
+  }
+
+  @Test
+  void encodeAndDecode_ValidInput_ValidOutput() {
+    // given
+    JwtConverter<Sample> jwtService = JwtConverter.<Sample>builder()
+        .clazz(Sample.class)
+        .jwtSecret(jwtSecret)
+        .objectMapperAsync(new ObjectMapperAsync(
+            new Jackson2JsonEncoder(),
+            new Jackson2JsonDecoder(),
+            new DefaultDataBufferFactory()))
+        .build();
+
+    Sample sample = new Sample();
+
+    // when
+    String jwt = jwtService.encode(sample).block();
+    Sample result = Objects.requireNonNull(jwtService.decode(jwt).block());
+
+    // then
+    then(result.field).isEqualTo("field");
+    then(result.zonedDateTime).isEqualTo(result.zonedDateTime);
+  }
+
+  @Test
+  void construct_shortJwtSecret_Exception() {
+    thenThrownBy(() -> JwtConverter.<Sample>builder()
+        .clazz(Sample.class)
+        .jwtSecret("shortJwtSecret")
+        .objectMapperAsync(new ObjectMapperAsync(
+            new Jackson2JsonEncoder(),
+            new Jackson2JsonDecoder(),
+            new DefaultDataBufferFactory()))
+        .build()
+    )
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessage("jwtSecret's length must be large or equal than 32");
+  }
+}

community-backend/settings.gradle

@@ -26,4 +26,5 @@ include 'in-system-available:common-web'
 
 include 'module:module-validation'
 include 'module:module-object-mapper-async'
+include 'core:core-jwt-converter'