hibernate-demo/src/test/java/com/ankurm/hibernatedemo/proxy/OsivDisabledExceptionTest.java

package com.ankurm.hibernatedemo.proxy;

import static org.assertj.core.api.Assertions.assertThat;

import jakarta.persistence.EntityManager;
import jakarta.persistence.EntityManagerFactory;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.system.CapturedOutput;
import org.springframework.boot.test.system.OutputCaptureExtension;
import org.springframework.boot.test.web.server.LocalServerPort;

/**
 * Backs docs/11-proxies-and-lazy-initialization.md, chapter "OSIV: the default, its warning, and what it actually
 * masks" -- the "off" half of {@link OsivDefaultWarningTest}. Same controller, same service,
 * same entity graph; only {@code spring.jpa.open-in-view} changes: the base
 * src/main/resources/application.yml already sets it to {@code false} explicitly, which this
 * test relies on and additionally restates for clarity.
 *
 * <p>The exception surfaces server-side (visible in the application log, asserted here via
 * {@link CapturedOutput}) even though the HTTP error body Boot's default
 * {@code BasicErrorController} returns is a bare
 * {@code {"timestamp":...,"status":500,"error":"Internal Server Error","path":...}} --
 * {@code server.error.include-message=always} does not surface it in the JSON body for this
 * failure mode, because the failure happens inside the {@code HttpMessageConverter} while
 * writing the response, which Boot reports as a generic 500 rather than routing the original
 * exception's message into the error attributes map. That gap is itself worth a line in the
 * article: don't rely on the HTTP response body to tell you WHY a 500 happened here -- check
 * the log.
 */
@ExtendWith(OutputCaptureExtension.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT, properties = {
        "spring.main.web-application-type=servlet",
        "spring.jpa.open-in-view=false"
})
class OsivDisabledExceptionTest {

    private static final Logger DEMO = LoggerFactory.getLogger("DEMO");

    @Autowired
    private EntityManagerFactory emf;

    @LocalServerPort
    private int port;

    private Long seedBookWithReview() {
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        ProxyPublisher publisher = new ProxyPublisher("OSIV Disabled Press");
        em.persist(publisher);
        ProxyBook book = new ProxyBook("OSIV Disabled Book", publisher);
        em.persist(book);
        ProxyReview review = new ProxyReview("Never rendered", book);
        em.persist(review);
        em.getTransaction().commit();
        Long id = book.getId();
        em.close();
        return id;
    }

    @Test
    void openInViewFalse_theSameControllerNowThrowsDuringSerialization(CapturedOutput output) throws Exception {
        Long id = seedBookWithReview();
        HttpClient client = HttpClient.newHttpClient();
        HttpResponse<String> response = client.send(
                HttpRequest.newBuilder(URI.create("http://localhost:" + port + "/osiv/books/" + id)).GET().build(),
                HttpResponse.BodyHandlers.ofString());

        DEMO.info("open-in-view=false: GET /osiv/books/{} -> status {}, body {}", id, response.statusCode(), response.body());

        assertThat(response.statusCode())
                .as("with OSIV off, the same request that worked in OsivDefaultWarningTest now fails")
                .isEqualTo(500);
        // Spring logs this as "Resolved [HttpMessageNotWritableException: Could not write
        // JSON: Cannot lazily initialize collection of role '...' (no session)]" -- the
        // OUTER exception is HttpMessageNotWritableException (thrown by the Jackson message
        // converter while writing the response body); LazyInitializationException's own
        // MESSAGE text is nested inside it, but the log line does not print
        // LazyInitializationException's class name. Assert on the message text that is
        // actually, verifiably there.
        assertThat(output.toString())
                .as("the real cause is visible server-side even though the HTTP error body is generic")
                .contains("HttpMessageNotWritableException")
                .contains("Cannot lazily initialize collection of role 'com.ankurm.hibernatedemo.proxy.ProxyBook.reviews'")
                .contains("(no session)");
    }
}