Support headers in DataBinding via constructor args

Closes gh-34073

Author: rstoyanchev

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/ExtendedWebExchangeDataBinder.java

@@ -24,6 +24,7 @@
 import org.springframework.http.HttpHeaders;
 import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
+import org.springframework.util.StringUtils;
 import org.springframework.web.bind.support.WebExchangeDataBinder;
 import org.springframework.web.reactive.HandlerMapping;
 import org.springframework.web.server.ServerWebExchange;
@@ -57,7 +58,11 @@ public Mono<Map<String, Object>> getValuesToBind(ServerWebExchange exchange) {
 			for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
 				List<String> values = entry.getValue();
 				if (!CollectionUtils.isEmpty(values)) {
-					String name = entry.getKey().replace("-", "");
+					// For constructor args with @BindParam mapped to the actual header name
+					String name = entry.getKey();
+					addValueIfNotPresent(map, "Header", name, (values.size() == 1 ? values.get(0) : values));
+					// Also adapt to Java conventions for setters
+					name = StringUtils.uncapitalize(entry.getKey().replace("-", ""));
 					addValueIfNotPresent(map, "Header", name, (values.size() == 1 ? values.get(0) : values));
 				}
 			}

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/InitBinderBindingContextTests.java

@@ -27,10 +27,12 @@
 import org.springframework.beans.testfixture.beans.TestBean;
 import org.springframework.core.DefaultParameterNameDiscoverer;
 import org.springframework.core.ReactiveAdapterRegistry;
+import org.springframework.core.ResolvableType;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.format.support.DefaultFormattingConversionService;
 import org.springframework.http.MediaType;
 import org.springframework.web.bind.WebDataBinder;
+import org.springframework.web.bind.annotation.BindParam;
 import org.springframework.web.bind.annotation.InitBinder;
 import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.support.ConfigurableWebBindingInitializer;
@@ -129,7 +131,7 @@ void createBinderTypeConversion() throws Exception {
 	}
 
 	@Test
-	void bindUriVariablesAndHeaders() throws Exception {
+	void bindUriVariablesAndHeadersViaSetters() throws Exception {
 
 		MockServerHttpRequest request = MockServerHttpRequest.get("/path")
 				.header("Some-Int-Array", "1")
@@ -153,6 +155,31 @@ void bindUriVariablesAndHeaders() throws Exception {
 		assertThat(target.getSomeIntArray()).containsExactly(1, 2);
 	}
 
+	@Test
+	void bindUriVariablesAndHeadersViaConstructor() throws Exception {
+
+		MockServerHttpRequest request = MockServerHttpRequest.get("/path")
+				.header("Some-Int-Array", "1")
+				.header("Some-Int-Array", "2")
+				.build();
+
+		MockServerWebExchange exchange = MockServerWebExchange.from(request);
+		exchange.getAttributes().put(
+				HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE,
+				Map.of("name", "John", "age", "25"));
+
+		BindingContext context = createBindingContext("initBinderWithAttributeName", WebDataBinder.class);
+		WebExchangeDataBinder binder = context.createDataBinder(exchange, null, "dataBean", null);
+		binder.setTargetType(ResolvableType.forClass(DataBean.class));
+		binder.construct(exchange).block();
+
+		DataBean bean = (DataBean) binder.getTarget();
+
+		assertThat(bean.name()).isEqualTo("John");
+		assertThat(bean.age()).isEqualTo(25);
+		assertThat(bean.someIntArray()).containsExactly(1, 2);
+	}
+
 	@Test
 	void bindUriVarsAndHeadersAddedConditionally() throws Exception {
 
@@ -212,4 +239,8 @@ public void initBinderTypeConversion(WebDataBinder dataBinder, @RequestParam int
 		}
 	}
 
+
+	private record DataBean(String name, int age, @BindParam("Some-Int-Array") Integer[] someIntArray) {
+	}
+
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ExtendedServletRequestDataBinder.java

@@ -156,6 +156,9 @@ protected Object getRequestParameter(String name, Class<?> type) {
 				if (uriVars != null) {
 					value = uriVars.get(name);
 				}
+				if (value == null && getRequest() instanceof HttpServletRequest httpServletRequest) {
+					value = getHeaderValue(httpServletRequest, name);
+				}
 			}
 			return value;
 		}
@@ -167,6 +170,13 @@ protected Set<String> initParameterNames(ServletRequest request) {
 			if (uriVars != null) {
 				set.addAll(uriVars.keySet());
 			}
+			if (request instanceof HttpServletRequest httpServletRequest) {
+				Enumeration<String> enumeration = httpServletRequest.getHeaderNames();
+				while (enumeration.hasMoreElements()) {
+					String headerName = enumeration.nextElement();
+					set.add(headerName.replaceAll("-", ""));
+				}
+			}
 			return set;
 		}
 	}

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ExtendedServletRequestDataBinderTests.java

@@ -22,7 +22,10 @@
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.testfixture.beans.TestBean;
+import org.springframework.core.ResolvableType;
 import org.springframework.web.bind.ServletRequestDataBinder;
+import org.springframework.web.bind.annotation.BindParam;
+import org.springframework.web.bind.support.BindParamNameResolver;
 import org.springframework.web.servlet.HandlerMapping;
 import org.springframework.web.testfixture.servlet.MockHttpServletRequest;
 
@@ -45,7 +48,7 @@ void setup() {
 
 
 	@Test
-	void createBinder() {
+	void createBinderViaSetters() {
 		request.setAttribute(
 				HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE,
 				Map.of("name", "John", "age", "25"));
@@ -62,6 +65,27 @@ void createBinder() {
 		assertThat(target.getSomeIntArray()).containsExactly(1, 2);
 	}
 
+	@Test
+	void createBinderViaConstructor() {
+		request.setAttribute(
+				HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE,
+				Map.of("name", "John", "age", "25"));
+
+		request.addHeader("Some-Int-Array", "1");
+		request.addHeader("Some-Int-Array", "2");
+
+		ServletRequestDataBinder binder = new ExtendedServletRequestDataBinder(null);
+		binder.setTargetType(ResolvableType.forClass(DataBean.class));
+		binder.setNameResolver(new BindParamNameResolver());
+		binder.construct(request);
+
+		DataBean bean = (DataBean) binder.getTarget();
+
+		assertThat(bean.name()).isEqualTo("John");
+		assertThat(bean.age()).isEqualTo(25);
+		assertThat(bean.someIntArray()).containsExactly(1, 2);
+	}
+
 	@Test
 	void uriVarsAndHeadersAddedConditionally() {
 		request.addParameter("name", "John");
@@ -88,4 +112,8 @@ void noUriTemplateVars() {
 		assertThat(target.getAge()).isEqualTo(0);
 	}
 
+
+	private record DataBean(String name, int age, @BindParam("Some-Int-Array") Integer[] someIntArray) {
+	}
+
 }