HttpUrl (OkHttp 3.1.1 API)

java.lang.Object
- okhttp3.HttpUrl

```
public final class HttpUrl
extends Object
```
A uniform resource locator (URL) with a scheme of either http or https. Use this class to compose and decompose Internet addresses. For example, this code will compose and print a URL for Google search:
```
   HttpUrl url = new HttpUrl.Builder()
       .scheme("https")
       .host("www.google.com")
       .addPathSegment("search")
       .addQueryParameter("q", "polar bears")
       .build();
   System.out.println(url);
 
```
which prints:
```
   https://www.google.com/search?q=polar%20bears
 
```
As another example, this code prints the human-readable query parameters of a Twitter search:
```
   HttpUrl url = HttpUrl.parse("https://twitter.com/search?q=cute%20%23puppies&f=images");
   for (int i = 0, size = url.querySize(); i < size; i++) {
     System.out.println(url.queryParameterName(i) + ": " + url.queryParameterValue(i));
   }
 
```
which prints:
```
   q: cute #puppies
   f: images
 
```
In addition to composing URLs from their component parts and decomposing URLs into their component parts, this class implements relative URL resolution: what address you'd reach by clicking a relative link on a specified page. For example:
```
   HttpUrl base = HttpUrl.parse("https://www.youtube.com/user/WatchTheDaily/videos");
   HttpUrl link = base.resolve("../../watch?v=cbP2N1BQdYc");
   System.out.println(link);
 
```
which prints:
```
   https://www.youtube.com/watch?v=cbP2N1BQdYc
 
```
What's in a URL?
A URL has several components.
Scheme

Sometimes referred to as protocol, A URL's scheme describes what mechanism should be used to retrieve the resource. Although URLs have many schemes (mailto, file, ftp), this class only supports http and https. Use java.net.URI for URLs with arbitrary schemes.
Username and Password

Username and password are either present, or the empty string "" if absent. This class offers no mechanism to differentiate empty from absent. Neither of these components are popular in practice. Typically HTTP applications use other mechanisms for user identification and authentication.
Host

The host identifies the webserver that serves the URL's resource. It is either a hostname like square.com or localhost, an IPv4 address like 192.168.0.1, or an IPv6 address like ::1.
Usually a webserver is reachable with multiple identifiers: its IP addresses, registered domain names, and even localhost when connecting from the server itself. Each of a webserver's names is a distinct URL and they are not interchangeable. For example, even if http://square.github.io/dagger and http://google.github.io/dagger are served by the same IP address, the two URLs identify different resources.
Port

The port used to connect to the webserver. By default this is 80 for HTTP and 443 for HTTPS. This class never returns -1 for the port: if no port is explicitly specified in the URL then the scheme's default is used.
Path

The path identifies a specific resource on the host. Paths have a hierarchical structure like "/square/okhttp/issues/1486". Each path segment is prefixed with "/". This class offers methods to compose and decompose paths by segment. If a path's last segment is the empty string, then the path ends with "/". This class always builds non-empty paths: if the path is omitted it defaults to "/", which is a path whose only segment is the empty string.
Query

The query is optional: it can be null, empty, or non-empty. For many HTTP URLs the query string is subdivided into a collection of name-value parameters. This class offers methods to set the query as the single string, or as individual name-value parameters. With name-value parameters the values are optional and names may be repeated.
Fragment

The fragment is optional: it can be null, empty, or non-empty. Unlike host, port, path, and query the fragment is not sent to the webserver: it's private to the client.
Encoding

Each component must be encoded before it is embedded in the complete URL. As we saw above, the string cute #puppies is encoded as cute%20%23puppies when used as a query parameter value.
Percent encoding

Percent encoding replaces a character (like 🍩) with its UTF-8 hex bytes (like %F0%9F%8D%A9). This approach works for whitespace characters, control characters, non-ASCII characters, and characters that already have another meaning in a particular context.
Percent encoding is used in every URL component except for the hostname. But the set of characters that need to be encoded is different for each component. For example, the path component must escape all of its ? characters, otherwise it could be interpreted as the start of the URL's query. But within the query and fragment components, the ? character doesn't delimit anything and doesn't need to be escaped.
```
   HttpUrl url = HttpUrl.parse("http://who-let-the-dogs.out").newBuilder()
       .addPathSegment("_Who?_")
       .query("_Who?_")
       .fragment("_Who?_")
       .build();
   System.out.println(url);
 
```
This prints:
```
   http://who-let-the-dogs.out/_Who%3F_?_Who?_#_Who?_
 
```
When parsing URLs that lack percent encoding where it is required, this class will percent encode the offending characters.
IDNA Mapping and Punycode encoding

Hostnames have different requirements and use a different encoding scheme. It consists of IDNA mapping and Punycode encoding.
In order to avoid confusion and discourage phishing attacks, IDNA Mapping transforms names to avoid confusing characters. This includes basic case folding: transforming shouting SQUARE.COM into cool and casual square.com. It also handles more exotic characters. For example, the Unicode trademark sign (™) could be confused for the letters "TM" in http://ho™mail.com. To mitigate this, the single character (™) maps to the string (tm). There is similar policy for all of the 1.1 million Unicode code points. Note that some code points such as "🍩" are not mapped and cannot be used in a hostname.
Punycode converts a Unicode string to an ASCII string to make international domain names work everywhere. For example, "σ" encodes as "xn--4xa". The encoded string is not human readable, but can be used with classes like InetAddress to establish connections.
Why another URL model?

Java includes both java.net.URL and java.net.URI. We offer a new URL model to address problems that the others don't.
Different URLs should be different

Although they have different content, java.net.URL considers the following two URLs equal, and the equals() method between them returns true:
- http://square.github.io/
- http://google.github.io/
This is because those two hosts share the same IP address. This is an old, bad design decision that makes java.net.URL unusable for many things. It shouldn't be used as a Map key or in a Set. Doing so is both inefficient because equality may require a DNS lookup, and incorrect because unequal URLs may be equal because of how they are hosted.
Equal URLs should be equal

These two URLs are semantically identical, but java.net.URI disagrees:
- http://host:80/
- http://host
Both the unnecessary port specification (:80) and the absent trailing slash (/) cause URI to bucket the two URLs separately. This harms URI's usefulness in collections. Any application that stores information-per-URL will need to either canonicalize manually, or suffer unnecessary redundancy for such URLs.
Because they don't attempt canonical form, these classes are surprisingly difficult to use securely. Suppose you're building a webservice that checks that incoming paths are prefixed "/static/images/" before serving the corresponding assets from the filesystem.
```
   String attack = "http://example.com/static/images/../../../../../etc/passwd";
   System.out.println(new URL(attack).getPath());
   System.out.println(new URI(attack).getPath());
   System.out.println(HttpUrl.parse(attack).path());
 
```
By canonicalizing the input paths, they are complicit in directory traversal attacks. Code that checks only the path prefix may suffer!
```
   /static/images/../../../../../etc/passwd
    /static/images/../../../../../etc/passwd
    /etc/passwd
 
```
If it works on the web, it should work in your application

The java.net.URI class is strict around what URLs it accepts. It rejects URLs like "http://example.com/abc|def" because the '|' character is unsupported. This class is more forgiving: it will automatically percent-encode the '|', yielding "http://example.com/abc%7Cdef". This kind behavior is consistent with web browsers. HttpUrl prefers consistency with major web browsers over consistency with obsolete specifications.
Paths and Queries should decompose

Neither of the built-in URL models offer direct access to path segments or query parameters. Manually using StringBuilder to assemble these components is cumbersome: do '+' characters get silently replaced with spaces? If a query parameter contains a '&', does that get escaped? By offering methods to read and write individual query parameters directly, application developers are saved from the hassles of encoding and decoding.
Plus a modern API

The URL (JDK1.0) and URI (Java 1.4) classes predate builders and instead use telescoping constructors. For example, there's no API to compose a URI with a custom port without also providing a query and fragment.
Instances of HttpUrl are well-formed and always have a scheme, host, and path. With java.net.URL it's possible to create an awkward URL like http:/ with scheme and path but no hostname. Building APIs that consume such malformed values is difficult!
This class has a modern API. It avoids punitive checked exceptions: parse() returns null if the input is an invalid URL. You can even be explicit about whether each component has been encoded already.

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class HttpUrl.Builder

Nested Classes
Modifier and Type	Class and Description
`static class`	`HttpUrl.Builder`

Method Summary

Methods
Modifier and Type	Method and Description
`static int`	`defaultPort(String scheme)` Returns 80 if `scheme.equals("http")`, 443 if `scheme.equals("https")` and -1 otherwise.
`String`	`encodedFragment()`
`String`	`encodedPassword()` Returns the password, or an empty string if none is set.
`String`	`encodedPath()` Returns the entire path of this URL, encoded for use in HTTP resource resolution.
`List<String>`	`encodedPathSegments()`
`String`	`encodedQuery()` Returns the query of this URL, encoded for use in HTTP resource resolution.
`String`	`encodedUsername()` Returns the username, or an empty string if none is set.
`boolean`	`equals(Object o)`
`String`	`fragment()`
`static HttpUrl`	`get(URI uri)`
`static HttpUrl`	`get(URL url)` Returns an `HttpUrl` for `url` if its protocol is `http` or `https`, or null if it has any other protocol.
`int`	`hashCode()`
`String`	`host()` Returns the host address suitable for use with `InetAddress.getAllByName(String)`.
`boolean`	`isHttps()`
`HttpUrl.Builder`	`newBuilder()`
`HttpUrl.Builder`	`newBuilder(String link)` Returns a builder for the URL that would be retrieved by following `link` from this URL, or null if the resulting URL is not well-formed.
`static HttpUrl`	`parse(String url)` Returns a new `HttpUrl` representing `url` if it is a well-formed HTTP or HTTPS URL, or null if it isn't.
`String`	`password()` Returns the decoded password, or an empty string if none is present.
`List<String>`	`pathSegments()`
`int`	`pathSize()`
`int`	`port()` Returns the explicitly-specified port if one was provided, or the default port for this URL's scheme.
`String`	`query()`
`String`	`queryParameter(String name)` Returns the first query parameter named `name` decoded using UTF-8, or null if there is no such query parameter.
`String`	`queryParameterName(int index)`
`Set<String>`	`queryParameterNames()`
`String`	`queryParameterValue(int index)`
`List<String>`	`queryParameterValues(String name)`
`int`	`querySize()`
`HttpUrl`	`resolve(String link)` Returns the URL that would be retrieved by following `link` from this URL, or null if the resulting URL is not well-formed.
`String`	`scheme()` Returns either "http" or "https".
`String`	`toString()`
`URI`	`uri()` Returns this URL as a `java.net.URI`.
`URL`	`url()` Returns this URL as a `java.net.URL`.
`String`	`username()`

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Method Detail
  - url
```
public URL url()
```
    Returns this URL as a java.net.URL.
  - uri
```
public URI uri()
```
    Returns this URL as a java.net.URI. Because URI is more strict than this class, the returned URI may be semantically different from this URL:
    - Characters forbidden by URI like [ and | will be escaped.
    - Invalid percent-encoded sequences like %xx will be encoded like %25xx.
    - Whitespace and control characters in the fragment will be stripped.
    These differences may have a significant consequence when the URI is interpretted by a webserver. For this reason the URI class and this method should be avoided.
  - scheme
```
public String scheme()
```
    Returns either "http" or "https".
  - isHttps
```
public boolean isHttps()
```
  - encodedUsername
```
public String encodedUsername()
```
    Returns the username, or an empty string if none is set.
  - username
```
public String username()
```
  - encodedPassword
```
public String encodedPassword()
```
    Returns the password, or an empty string if none is set.
  - password
```
public String password()
```
    Returns the decoded password, or an empty string if none is present.
  - host
```
public String host()
```
    Returns the host address suitable for use with InetAddress.getAllByName(String). May be:
    - A regular host name, like android.com.
    - An IPv4 address, like 127.0.0.1.
    - An IPv6 address, like ::1. Note that there are no square braces.
    - An encoded IDN, like xn--n3h.net.
  - port
```
public int port()
```
    Returns the explicitly-specified port if one was provided, or the default port for this URL's scheme. For example, this returns 8443 for https://square.com:8443/ and 443 for https://square.com/. The result is in [1..65535].
  - defaultPort
```
public static int defaultPort(String scheme)
```
    Returns 80 if scheme.equals("http"), 443 if scheme.equals("https") and -1 otherwise.
  - pathSize
```
public int pathSize()
```
  - encodedPath
```
public String encodedPath()
```
    Returns the entire path of this URL, encoded for use in HTTP resource resolution. The returned path is always nonempty and is prefixed with /.
  - encodedPathSegments
```
public List<String> encodedPathSegments()
```
  - pathSegments
```
public List<String> pathSegments()
```
  - encodedQuery
```
public String encodedQuery()
```
    Returns the query of this URL, encoded for use in HTTP resource resolution. The returned string may be null (for URLs with no query), empty (for URLs with an empty query) or non-empty (all other URLs).
  - query
```
public String query()
```
  - querySize
```
public int querySize()
```
  - queryParameter
```
public String queryParameter(String name)
```
    Returns the first query parameter named name decoded using UTF-8, or null if there is no such query parameter.
  - queryParameterNames
```
public Set<String> queryParameterNames()
```
  - queryParameterValues
```
public List<String> queryParameterValues(String name)
```
  - queryParameterName
```
public String queryParameterName(int index)
```
  - queryParameterValue
```
public String queryParameterValue(int index)
```
  - encodedFragment
```
public String encodedFragment()
```
  - fragment
```
public String fragment()
```
  - resolve
```
public HttpUrl resolve(String link)
```
    Returns the URL that would be retrieved by following link from this URL, or null if the resulting URL is not well-formed.
  - newBuilder
```
public HttpUrl.Builder newBuilder()
```
  - newBuilder
```
public HttpUrl.Builder newBuilder(String link)
```
    Returns a builder for the URL that would be retrieved by following link from this URL, or null if the resulting URL is not well-formed.
  - parse
```
public static HttpUrl parse(String url)
```
    Returns a new HttpUrl representing url if it is a well-formed HTTP or HTTPS URL, or null if it isn't.
  - get
```
public static HttpUrl get(URL url)
```
    Returns an HttpUrl for url if its protocol is http or https, or null if it has any other protocol.
  - get
```
public static HttpUrl get(URI uri)
```
  - equals
```
public boolean equals(Object o)
```
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class HttpUrl

What's in a URL?

Scheme

Username and Password

Host

Port

Path

Query

Fragment

Encoding

Percent encoding

IDNA Mapping and Punycode encoding

Why another URL model?

Different URLs should be different

Equal URLs should be equal

If it works on the web, it should work in your application

Paths and Queries should decompose

Plus a modern API

Nested Class Summary

Method Summary

Methods inherited from class java.lang.Object

Method Detail

url

uri

scheme

isHttps

encodedUsername

username

encodedPassword

password

host

port

defaultPort

pathSize

encodedPath

encodedPathSegments

pathSegments

encodedQuery

query

querySize

queryParameter

queryParameterNames

queryParameterValues

queryParameterName

queryParameterValue

encodedFragment

fragment

resolve

newBuilder

newBuilder

parse

get

get

equals

hashCode

toString