add PublicJwtService

src/main/kotlin/ltd/hlaeja/jwt/service/PublicJwtService.kt

@@ -0,0 +1,28 @@
+package ltd.hlaeja.jwt.service
+
+import io.jsonwebtoken.Claims
+import io.jsonwebtoken.Jws
+import io.jsonwebtoken.JwtParser
+import io.jsonwebtoken.Jwts
+import ltd.hlaeja.jwt.util.PublicKeyProvider
+import org.springframework.beans.factory.annotation.Value
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty
+import org.springframework.stereotype.Service
+
+@Service
+@ConditionalOnProperty(prefix = "jwt", name = ["public-key"])
+class PublicJwtService(
+    @Value("\${jwt.public-key}")
+    jwtPublicKey: String,
+) {
+
+    private val parser: JwtParser = Jwts.parser()
+        .verifyWith(PublicKeyProvider.load(jwtPublicKey))
+        .build()
+
+    fun <T> verify(
+        token: String,
+        block: (claims: Jws<Claims>) -> T,
+    ): T = parser.parseSignedClaims(token)
+        .let(block)
+}

src/test/kotlin/ltd/hlaeja/jwt/service/PublicJwtServiceTest.kt

@@ -0,0 +1,36 @@
+package ltd.hlaeja.jwt.service
+
+import java.nio.charset.StandardCharsets.UTF_8
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.springframework.core.io.ClassPathResource
+import org.springframework.util.FileCopyUtils
+
+class PublicJwtServiceTest {
+
+    private lateinit var service: PublicJwtService
+
+    @BeforeEach
+    fun setup() {
+        service = PublicJwtService("cert/valid-public-key.pem")
+    }
+
+    @Test
+    fun `parse token with claims`() {
+        // given
+        val token = String(FileCopyUtils.copyToByteArray(ClassPathResource("jwt.token").inputStream), UTF_8).trim()
+
+        // when
+        val result = service.verify(token) { claims ->
+            mapOf(
+                "claim1" to claims.payload["claim1"] as String,
+                "claim2" to claims.payload["claim2"] as Int,
+            )
+        }
+
+        // then
+        assertThat(result["claim1"]).isEqualTo("value1")
+        assertThat(result["claim2"]).isEqualTo(123)
+    }
+}