[[uricomponents]]
= UriComponents
[.small]#Spring MVC and Spring WebFlux#

`UriComponentsBuilder` helps to build URI's from URI templates with variables, as the following example shows:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	UriComponents uriComponents = UriComponentsBuilder
			.fromUriString("https://example.com/hotels/{hotel}") // <1>
			.queryParam("q", "{q}") // <2>
			.encode() // <3>
			.build(); // <4>

	URI uri = uriComponents.expand("Westin", "123").toUri(); // <5>
----
<1> Static factory method with a URI template.
<2> Add or replace URI components.
<3> Request to have the URI template and URI variables encoded.
<4> Build a `UriComponents`.
<5> Expand variables and obtain the `URI`.

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	val uriComponents = UriComponentsBuilder
			.fromUriString("https://example.com/hotels/{hotel}") // <1>
			.queryParam("q", "{q}") // <2>
			.encode() // <3>
			.build() // <4>

	val uri = uriComponents.expand("Westin", "123").toUri() // <5>
----
<1> Static factory method with a URI template.
<2> Add or replace URI components.
<3> Request to have the URI template and URI variables encoded.
<4> Build a `UriComponents`.
<5> Expand variables and obtain the `URI`.
======

The preceding example can be consolidated into one chain and shortened with `buildAndExpand`,
as the following example shows:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	URI uri = UriComponentsBuilder
			.fromUriString("https://example.com/hotels/{hotel}")
			.queryParam("q", "{q}")
			.encode()
			.buildAndExpand("Westin", "123")
			.toUri();
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	val uri = UriComponentsBuilder
			.fromUriString("https://example.com/hotels/{hotel}")
			.queryParam("q", "{q}")
			.encode()
			.buildAndExpand("Westin", "123")
			.toUri()
----
======

You can shorten it further by going directly to a URI (which implies encoding),
as the following example shows:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	URI uri = UriComponentsBuilder
			.fromUriString("https://example.com/hotels/{hotel}")
			.queryParam("q", "{q}")
			.build("Westin", "123");
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	val uri = UriComponentsBuilder
			.fromUriString("https://example.com/hotels/{hotel}")
			.queryParam("q", "{q}")
			.build("Westin", "123")
----
======

You can shorten it further still with a full URI template, as the following example shows:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	URI uri = UriComponentsBuilder
			.fromUriString("https://example.com/hotels/{hotel}?q={q}")
			.build("Westin", "123");
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	val uri = UriComponentsBuilder
			.fromUriString("https://example.com/hotels/{hotel}?q={q}")
			.build("Westin", "123")
----
======



[[uribuilder]]
= UriBuilder
[.small]#Spring MVC and Spring WebFlux#

<<web-uricomponents, `UriComponentsBuilder`>> implements `UriBuilder`. You can create a
`UriBuilder`, in turn, with a `UriBuilderFactory`. Together, `UriBuilderFactory` and
`UriBuilder` provide a pluggable mechanism to build URIs from URI templates, based on
shared configuration, such as a base URL, encoding preferences, and other details.

You can configure `RestTemplate` and `WebClient` with a `UriBuilderFactory`
to customize the preparation of URIs. `DefaultUriBuilderFactory` is a default
implementation of `UriBuilderFactory` that uses `UriComponentsBuilder` internally and
exposes shared configuration options.

The following example shows how to configure a `RestTemplate`:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	// import org.springframework.web.util.DefaultUriBuilderFactory.EncodingMode;

	String baseUrl = "https://example.org";
	DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory(baseUrl);
	factory.setEncodingMode(EncodingMode.TEMPLATE_AND_VALUES);

	RestTemplate restTemplate = new RestTemplate();
	restTemplate.setUriTemplateHandler(factory);
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	// import org.springframework.web.util.DefaultUriBuilderFactory.EncodingMode

	val baseUrl = "https://example.org"
	val factory = DefaultUriBuilderFactory(baseUrl)
	factory.encodingMode = EncodingMode.TEMPLATE_AND_VALUES

	val restTemplate = RestTemplate()
	restTemplate.uriTemplateHandler = factory
----
======

The following example configures a `WebClient`:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	// import org.springframework.web.util.DefaultUriBuilderFactory.EncodingMode;

	String baseUrl = "https://example.org";
	DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory(baseUrl);
	factory.setEncodingMode(EncodingMode.TEMPLATE_AND_VALUES);

	WebClient client = WebClient.builder().uriBuilderFactory(factory).build();
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	// import org.springframework.web.util.DefaultUriBuilderFactory.EncodingMode

	val baseUrl = "https://example.org"
	val factory = DefaultUriBuilderFactory(baseUrl)
	factory.encodingMode = EncodingMode.TEMPLATE_AND_VALUES

	val client = WebClient.builder().uriBuilderFactory(factory).build()
----
======

In addition, you can also use `DefaultUriBuilderFactory` directly. It is similar to using
`UriComponentsBuilder` but, instead of static factory methods, it is an actual instance
that holds configuration and preferences, as the following example shows:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	String baseUrl = "https://example.com";
	DefaultUriBuilderFactory uriBuilderFactory = new DefaultUriBuilderFactory(baseUrl);

	URI uri = uriBuilderFactory.uriString("/hotels/{hotel}")
			.queryParam("q", "{q}")
			.build("Westin", "123");
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	val baseUrl = "https://example.com"
	val uriBuilderFactory = DefaultUriBuilderFactory(baseUrl)

	val uri = uriBuilderFactory.uriString("/hotels/{hotel}")
			.queryParam("q", "{q}")
			.build("Westin", "123")
----
======


[[uri-parsing]]
= URI Parsing
[.small]#Spring MVC and Spring WebFlux#

`UriComponentsBuilder` supports two URI parser types:

1. RFC parser -- this parser type expects URI strings to conform to RFC 3986 syntax,
and treats deviations from the syntax as illegal.

2. WhatWG parser -- this parser is based on the
https://github.com/web-platform-tests/wpt/tree/master/url[URL parsing algorithm] in the
https://url.spec.whatwg.org[WhatWG URL Living standard]. It provides lenient handling of
a wide range of cases of unexpected input. Browsers implement this in order to handle
leniently user typed URL's. For more details, see the URL Living Standard and URL parsing
https://github.com/web-platform-tests/wpt/tree/master/url[test cases].

By default, `RestClient`, `WebClient`, and `RestTemplate` use the RFC parser type, and
expect applications to provide with URL templates that conform to RFC syntax. To change
that you can customize the `UriBuilderFactory` on any of the clients.

Applications and frameworks may further rely on `UriComponentsBuilder` for their own needs
to parse user provided URL's in order to inspect and possibly validated URI components
such as the scheme, host, port, path, and query. Such components can decide to use the
WhatWG parser type in order to handle URL's more leniently, and to align with the way
browsers parse URI's, in case of a redirect to the input URL or if it is included in a
response to a browser.


[[uri-encoding]]
= URI Encoding
[.small]#Spring MVC and Spring WebFlux#

`UriComponentsBuilder` exposes encoding options at two levels:

* {spring-framework-api}/web/util/UriComponentsBuilder.html#encode--[UriComponentsBuilder#encode()]:
Pre-encodes the URI template first and then strictly encodes URI variables when expanded.
* {spring-framework-api}/web/util/UriComponents.html#encode--[UriComponents#encode()]:
Encodes URI components _after_ URI variables are expanded.

Both options replace non-ASCII and illegal characters with escaped octets. However, the first option
also replaces characters with reserved meaning that appear in URI variables.

TIP: Consider ";", which is legal in a path but has reserved meaning. The first option replaces
";" with "%3B" in URI variables but not in the URI template. By contrast, the second option never
replaces ";", since it is a legal character in a path.

For most cases, the first option is likely to give the expected result, because it treats URI
variables as opaque data to be fully encoded, while the second option is useful if URI
variables do intentionally contain reserved characters. The second option is also useful
when not expanding URI variables at all since that will also encode anything that
incidentally looks like a URI variable.

The following example uses the first option:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	URI uri = UriComponentsBuilder.fromPath("/hotel list/{city}")
			.queryParam("q", "{q}")
			.encode()
			.buildAndExpand("New York", "foo+bar")
			.toUri();

	// Result is "/hotel%20list/New%20York?q=foo%2Bbar"
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	val uri = UriComponentsBuilder.fromPath("/hotel list/{city}")
			.queryParam("q", "{q}")
			.encode()
			.buildAndExpand("New York", "foo+bar")
			.toUri()

	// Result is "/hotel%20list/New%20York?q=foo%2Bbar"
----
======

You can shorten the preceding example by going directly to the URI (which implies encoding),
as the following example shows:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	URI uri = UriComponentsBuilder.fromPath("/hotel list/{city}")
			.queryParam("q", "{q}")
			.build("New York", "foo+bar");
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	val uri = UriComponentsBuilder.fromPath("/hotel list/{city}")
			.queryParam("q", "{q}")
			.build("New York", "foo+bar")
----
======

You can shorten it further still with a full URI template, as the following example shows:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	URI uri = UriComponentsBuilder.fromUriString("/hotel list/{city}?q={q}")
			.build("New York", "foo+bar");
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	val uri = UriComponentsBuilder.fromUriString("/hotel list/{city}?q={q}")
			.build("New York", "foo+bar")
----
======

The `WebClient` and the `RestTemplate` expand and encode URI templates internally through
the `UriBuilderFactory` strategy. Both can be configured with a custom strategy,
as the following example shows:

[tabs]
======
Java::
+
[source,java,indent=0,subs="verbatim,quotes"]
----
	String baseUrl = "https://example.com";
	DefaultUriBuilderFactory factory = new DefaultUriBuilderFactory(baseUrl)
	factory.setEncodingMode(EncodingMode.TEMPLATE_AND_VALUES);

	// Customize the RestTemplate..
	RestTemplate restTemplate = new RestTemplate();
	restTemplate.setUriTemplateHandler(factory);

	// Customize the WebClient..
	WebClient client = WebClient.builder().uriBuilderFactory(factory).build();
----

Kotlin::
+
[source,kotlin,indent=0,subs="verbatim,quotes"]
----
	val baseUrl = "https://example.com"
	val factory = DefaultUriBuilderFactory(baseUrl).apply {
		encodingMode = EncodingMode.TEMPLATE_AND_VALUES
	}

	// Customize the RestTemplate..
	val restTemplate = RestTemplate().apply {
		uriTemplateHandler = factory
	}

	// Customize the WebClient..
	val client = WebClient.builder().uriBuilderFactory(factory).build()
----
======

The `DefaultUriBuilderFactory` implementation uses `UriComponentsBuilder` internally to
expand and encode URI templates. As a factory, it provides a single place to configure
the approach to encoding, based on one of the below encoding modes:

* `TEMPLATE_AND_VALUES`: Uses `UriComponentsBuilder#encode()`, corresponding to
the first option in the earlier list, to pre-encode the URI template and strictly encode URI variables when
expanded.
* `VALUES_ONLY`: Does not encode the URI template and, instead, applies strict encoding
to URI variables through `UriUtils#encodeUriVariables` prior to expanding them into the
template.
* `URI_COMPONENT`: Uses `UriComponents#encode()`, corresponding to the second option in the earlier list, to
encode URI component value _after_ URI variables are expanded.
* `NONE`: No encoding is applied.

The `RestTemplate` is set to `EncodingMode.URI_COMPONENT` for historical
reasons and for backwards compatibility. The `WebClient` relies on the default value
in `DefaultUriBuilderFactory`, which was changed from `EncodingMode.URI_COMPONENT` in
5.0.x to `EncodingMode.TEMPLATE_AND_VALUES` in 5.1.
