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本文主要研究一下SpringBootTest的webEnvironment

SpringBootTest

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@BootstrapWith(SpringBootTestContextBootstrapper.class)
@ExtendWith({SpringExtension.class})
public @interface SpringBootTest {
    @AliasFor("properties")
    String[] value() default {};

    @AliasFor("value")
    String[] properties() default {};

    String[] args() default {};

    Class<?>[] classes() default {};

    WebEnvironment webEnvironment() default SpringBootTest.WebEnvironment.MOCK;
}    

SpringBootTest的webEnvironment默认为SpringBootTest.WebEnvironment.MOCK

WebEnvironment

	/**
	 * An enumeration web environment modes.
	 */
	enum WebEnvironment {

		/**
		 * Creates a {@link WebApplicationContext} with a mock servlet environment if
		 * servlet APIs are on the classpath, a {@link ReactiveWebApplicationContext} if
		 * Spring WebFlux is on the classpath or a regular {@link ApplicationContext}
		 * otherwise.
		 */
		MOCK(false),

		/**
		 * Creates a web application context (reactive or servlet based) and sets a
		 * {@code server.port=0} {@link Environment} property (which usually triggers
		 * listening on a random port). Often used in conjunction with a
		 * {@link LocalServerPort @LocalServerPort} injected field on the test.
		 */
		RANDOM_PORT(true),

		/**
		 * Creates a (reactive) web application context without defining any
		 * {@code server.port=0} {@link Environment} property.
		 */
		DEFINED_PORT(true),

		/**
		 * Creates an {@link ApplicationContext} and sets
		 * {@link SpringApplication#setWebApplicationType(WebApplicationType)} to
		 * {@link WebApplicationType#NONE}.
		 */
		NONE(false);

		private final boolean embedded;

		WebEnvironment(boolean embedded) {
			this.embedded = embedded;
		}

		/**
		 * Return if the environment uses an {@link ServletWebServerApplicationContext}.
		 * @return if an {@link ServletWebServerApplicationContext} is used.
		 */
		public boolean isEmbedded() {
			return this.embedded;
		}

	}

WebEnvironment有四个枚举，分别是MOCK、RANDOM_PORT、DEFINED_PORT、NONE

SpringBootTestContextBootstrapper

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/SpringBootTestContextBootstrapper.java

public class SpringBootTestContextBootstrapper extends DefaultTestContextBootstrapper {

	private static final String[] WEB_ENVIRONMENT_CLASSES = { "javax.servlet.Servlet",
			"org.springframework.web.context.ConfigurableWebApplicationContext" };

	private static final String REACTIVE_WEB_ENVIRONMENT_CLASS = "org.springframework."
			+ "web.reactive.DispatcherHandler";

	private static final String MVC_WEB_ENVIRONMENT_CLASS = "org.springframework.web.servlet.DispatcherServlet";

	private static final String JERSEY_WEB_ENVIRONMENT_CLASS = "org.glassfish.jersey.server.ResourceConfig";

	private static final String ACTIVATE_SERVLET_LISTENER = "org.springframework.test."
			+ "context.web.ServletTestExecutionListener.activateListener";

	private static final Log logger = LogFactory.getLog(SpringBootTestContextBootstrapper.class);

	@Override
	public TestContext buildTestContext() {
		TestContext context = super.buildTestContext();
		verifyConfiguration(context.getTestClass());
		WebEnvironment webEnvironment = getWebEnvironment(context.getTestClass());
		if (webEnvironment == WebEnvironment.MOCK && deduceWebApplicationType() == WebApplicationType.SERVLET) {
			context.setAttribute(ACTIVATE_SERVLET_LISTENER, true);
		}
		else if (webEnvironment != null && webEnvironment.isEmbedded()) {
			context.setAttribute(ACTIVATE_SERVLET_LISTENER, false);
		}
		return context;
	}

	//......
}

SpringBootTestContextBootstrapper继承了DefaultTestContextBootstrapper，其buildTestContext方法会判断webEnvironment，然后决定ACTIVATE_SERVLET_LISTENER是设置为true还是false，在为MOCK的时候该值为true

ServletTestExecutionListener

spring-test/src/main/java/org/springframework/test/context/web/ServletTestExecutionListener.java

    private boolean isActivated(TestContext testContext) {
        return Boolean.TRUE.equals(testContext.getAttribute(ACTIVATE_LISTENER)) || AnnotatedElementUtils.hasAnnotation(testContext.getTestClass(), WebAppConfiguration.class);
    }

    private void setUpRequestContextIfNecessary(TestContext testContext) {
		if (!isActivated(testContext) || alreadyPopulatedRequestContextHolder(testContext)) {
			return;
		}

		ApplicationContext context = testContext.getApplicationContext();

		if (context instanceof WebApplicationContext) {
			WebApplicationContext wac = (WebApplicationContext) context;
			ServletContext servletContext = wac.getServletContext();
			Assert.state(servletContext instanceof MockServletContext, () -> String.format(
						"The WebApplicationContext for test context %s must be configured with a MockServletContext.",
						testContext));

			if (logger.isDebugEnabled()) {
				logger.debug(String.format(
						"Setting up MockHttpServletRequest, MockHttpServletResponse, ServletWebRequest, and RequestContextHolder for test context %s.",
						testContext));
			}

			MockServletContext mockServletContext = (MockServletContext) servletContext;
			MockHttpServletRequest request = new MockHttpServletRequest(mockServletContext);
			request.setAttribute(CREATED_BY_THE_TESTCONTEXT_FRAMEWORK, Boolean.TRUE);
			MockHttpServletResponse response = new MockHttpServletResponse();
			ServletWebRequest servletWebRequest = new ServletWebRequest(request, response);

			RequestContextHolder.setRequestAttributes(servletWebRequest);
			testContext.setAttribute(POPULATED_REQUEST_CONTEXT_HOLDER_ATTRIBUTE, Boolean.TRUE);
			testContext.setAttribute(RESET_REQUEST_CONTEXT_HOLDER_ATTRIBUTE, Boolean.TRUE);

			if (wac instanceof ConfigurableApplicationContext) {
				@SuppressWarnings("resource")
				ConfigurableApplicationContext configurableApplicationContext = (ConfigurableApplicationContext) wac;
				ConfigurableListableBeanFactory bf = configurableApplicationContext.getBeanFactory();
				bf.registerResolvableDependency(MockHttpServletResponse.class, response);
				bf.registerResolvableDependency(ServletWebRequest.class, servletWebRequest);
			}
		}
	}

ServletTestExecutionListener的isActivated会判断ACTIVATE_SERVLET_LISTENER是不是设置为true，或者testClass有标注@WebAppConfiguration; setUpRequestContextIfNecessary方法会调用isActivated来决定是否初始化MockHttpServletRequest等设置

小结

SpringBootTest的webEnvironment默认为SpringBootTest.WebEnvironment.MOCK，它会设置ACTIVATE_SERVLET_LISTENER是设置为true，即在ServletTestExecutionListener的isActivated为true，在setUpRequestContextIfNecessary方法会初始化MockHttpServletRequest、MockHttpServletResponse等。