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URI Links

This section describes various options available in the Spring Framework to work with URI’s.

Relative Servlet Requests

You can use ServletUriComponentsBuilder to create URIs relative to the current request, as the following example shows:

Java
HttpServletRequest request = ...

// Re-uses scheme, host, port, path, and query string...

URI uri = ServletUriComponentsBuilder.fromRequest(request)
		.replaceQueryParam("accountId", "{id}")
		.build("123");
Kotlin
val request: HttpServletRequest = ...

// Re-uses scheme, host, port, path, and query string...

val uri = ServletUriComponentsBuilder.fromRequest(request)
		.replaceQueryParam("accountId", "{id}")
		.build("123")

You can create URIs relative to the context path, as the following example shows:

Java
HttpServletRequest request = ...

// Re-uses scheme, host, port, and context path...

URI uri = ServletUriComponentsBuilder.fromContextPath(request)
		.path("/accounts")
		.build()
		.toUri();
Kotlin
val request: HttpServletRequest = ...

// Re-uses scheme, host, port, and context path...

val uri = ServletUriComponentsBuilder.fromContextPath(request)
		.path("/accounts")
		.build()
		.toUri()

You can create URIs relative to a Servlet (for example, /main/*), as the following example shows:

Java
HttpServletRequest request = ...

// Re-uses scheme, host, port, context path, and Servlet mapping prefix...

URI uri = ServletUriComponentsBuilder.fromServletMapping(request)
		.path("/accounts")
		.build()
		.toUri();
Kotlin
val request: HttpServletRequest = ...

// Re-uses scheme, host, port, context path, and Servlet mapping prefix...

val uri = ServletUriComponentsBuilder.fromServletMapping(request)
		.path("/accounts")
		.build()
		.toUri()
Note
 As of 5.1, ServletUriComponentsBuilder ignores information from the Forwarded and X-Forwarded-* headers, which specify the client-originated address. Consider using the ForwardedHeaderFilter to extract and use or to discard such headers.

Links to Controllers

Spring MVC provides a mechanism to prepare links to controller methods. For example, the following MVC controller allows for link creation:

Java
@Controller
@RequestMapping("/hotels/{hotel}")
public class BookingController {

	@GetMapping("/bookings/{booking}")
	public ModelAndView getBooking(@PathVariable Long booking) {
		// ...
	}
}
Kotlin
@Controller
@RequestMapping("/hotels/{hotel}")
class BookingController {

	@GetMapping("/bookings/{booking}")
	fun getBooking(@PathVariable booking: Long): ModelAndView {
		// ...
	}
}

You can prepare a link by referring to the method by name, as the following example shows:

Java
UriComponents uriComponents = MvcUriComponentsBuilder
	.fromMethodName(BookingController.class, "getBooking", 21).buildAndExpand(42);

URI uri = uriComponents.encode().toUri();
Kotlin
val uriComponents = MvcUriComponentsBuilder
	.fromMethodName(BookingController::class.java, "getBooking", 21).buildAndExpand(42)

val uri = uriComponents.encode().toUri()

In the preceding example, we provide actual method argument values (in this case, the long value: 21) to be used as a path variable and inserted into the URL. Furthermore, we provide the value, 42, to fill in any remaining URI variables, such as the hotel variable inherited from the type-level request mapping. If the method had more arguments, we could supply null for arguments not needed for the URL. In general, only @PathVariable and @RequestParam arguments are relevant for constructing the URL.

There are additional ways to use MvcUriComponentsBuilder. For example, you can use a technique akin to mock testing through proxies to avoid referring to the controller method by name, as the following example shows (the example assumes static import of MvcUriComponentsBuilder.on):

Java
UriComponents uriComponents = MvcUriComponentsBuilder
	.fromMethodCall(on(BookingController.class).getBooking(21)).buildAndExpand(42);

URI uri = uriComponents.encode().toUri();
Kotlin
val uriComponents = MvcUriComponentsBuilder
	.fromMethodCall(on(BookingController::class.java).getBooking(21)).buildAndExpand(42)

val uri = uriComponents.encode().toUri()
Note
 Controller method signatures are limited in their design when they are supposed to be usable for link creation with fromMethodCall. Aside from needing a proper parameter signature, there is a technical limitation on the return type (namely, generating a runtime proxy for link builder invocations), so the return type must not be final. In particular, the common String return type for view names does not work here. You should use ModelAndView or even plain Object (with a String return value) instead.

The earlier examples use static methods in MvcUriComponentsBuilder. Internally, they rely on ServletUriComponentsBuilder to prepare a base URL from the scheme, host, port, context path, and servlet path of the current request. This works well in most cases. However, sometimes, it can be insufficient. For example, you may be outside the context of a request (such as a batch process that prepares links) or perhaps you need to insert a path prefix (such as a locale prefix that was removed from the request path and needs to be re-inserted into links).

For such cases, you can use the static fromXxx overloaded methods that accept a UriComponentsBuilder to use a base URL. Alternatively, you can create an instance of MvcUriComponentsBuilder with a base URL and then use the instance-based withXxx methods. For example, the following listing uses withMethodCall:

Java
UriComponentsBuilder base = ServletUriComponentsBuilder.fromCurrentContextPath().path("/en");
MvcUriComponentsBuilder builder = MvcUriComponentsBuilder.relativeTo(base);
builder.withMethodCall(on(BookingController.class).getBooking(21)).buildAndExpand(42);

URI uri = uriComponents.encode().toUri();
Kotlin
val base = ServletUriComponentsBuilder.fromCurrentContextPath().path("/en")
val builder = MvcUriComponentsBuilder.relativeTo(base)
builder.withMethodCall(on(BookingController::class.java).getBooking(21)).buildAndExpand(42)

val uri = uriComponents.encode().toUri()
Note
 As of 5.1, MvcUriComponentsBuilder ignores information from the Forwarded and X-Forwarded-* headers, which specify the client-originated address. Consider using the ForwardedHeaderFilter to extract and use or to discard such headers.

Links in Views

In views such as Thymeleaf, FreeMarker, or JSP, you can build links to annotated controllers by referring to the implicitly or explicitly assigned name for each request mapping.

Consider the following example:

Java
@RequestMapping("/people/{id}/addresses")
public class PersonAddressController {

	@RequestMapping("/{country}")
	public HttpEntity<PersonAddress> getAddress(@PathVariable String country) { ... }
}
Kotlin
@RequestMapping("/people/{id}/addresses")
class PersonAddressController {

	@RequestMapping("/{country}")
	fun getAddress(@PathVariable country: String): HttpEntity<PersonAddress> { ... }
}

Given the preceding controller, you can prepare a link from a JSP, as follows:

<%@ taglib uri="http://www.springframework.org/tags" prefix="s" %>
...
<a href="${s:mvcUrl('PAC#getAddress').arg(0,'US').buildAndExpand('123')}">Get Address</a>

The preceding example relies on the mvcUrl function declared in the Spring tag library (that is, META-INF/spring.tld), but it is easy to define your own function or prepare a similar one for other templating technologies.

Here is how this works. On startup, every @RequestMapping is assigned a default name through HandlerMethodMappingNamingStrategy, whose default implementation uses the capital letters of the class and the method name (for example, the getThing method in ThingController becomes "TC#getThing"). If there is a name clash, you can use @RequestMapping(name="..") to assign an explicit name or implement your own HandlerMethodMappingNamingStrategy.