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Java url add params

Содержание
  1. Java url add params
  2. Add query parameters Apache HttpClient
  3. Creating a URL
  4. Creating a URL Relative to Another
  5. Other URL Constructors
  6. URL addresses with Special characters
  7. MalformedURLException
  8. Передача сложных объектов в параметрах URL

Java url add params

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Add query parameters Apache HttpClient

Here,
param1, param2 and param3 are called Query parameters or Request parameters.

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In this article, we will look at adding query parameters to a request URL in Apache HttpClient library in java.
If you do know how to send an HTTP request with HttpClient, refer this article.

URIBuilder
Apache HttpClient provides a URIBuilder class which accepts a base URL as constructor argument.
For adding query parameters, it provides addParameter() method, which takes two string arguments representing parameter name and value.

After the parameters are added to the URIBuilder , call its build() method to create an object of URI class.
This URI object is provided to the request using its setURI() method.

HttpPost post = new HttpPost("https://app-url"); URI uriBuilder = new URIBuilder(post.getURI()). addParameter("id", "10"). addParameter("name", "abc").build(); post.setURI(uriBuilder);

If you look at the logs, then you would see below line

20:16:54.250 [main] DEBUG org.apache.http.headers – http-outgoing-0 which shows that it has successfully added query parameters to the URL.

Note that in above example, base URL for URIBuilder is taken from request object using its getURI() method.
But, we can also set the base URL directly in the URIBuilder constructor as shown below

HttpPost post = new HttpPost(); URI uriBuilder = new URIBuilder("https://app-url"). addParameter("id", "10"). addParameter("name", "abc").build(); post.setURI(uriBuilder);

This also has the same result.

This method is applicable to both GET and POST request objects of HttpClient.
Adding all parameters
URIBuilder provides an option to add multiple query parameters at once, instead of calling addParameter() multiple times.
It has an addParameters() method which takes a list of NameValuePair objects. Example,

HttpPost post = new HttpPost("https://app-url"); // define a list List parameters = new ArrayList<>(); // add new parameters parameters.add(new BasicNameValuePair("id", "10")); parameters.add(new BasicNameValuePair("name", "abc")); URI uriBuilder = new URIBuilder(post.getURI()). addParameters(parameters). build(); post.setURI(uriBuilder);

NameValuePair is an interface , so we create object of BasicNameValuePair , which implements it.

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Creating a URL

The easiest way to create a URL object is from a String that represents the human-readable form of the URL address. This is typically the form that another person will use for a URL. In your Java program, you can use a String containing this text to create a URL object:

URL myURL = new URL("http://example.com/");

The URL object created above represents an absolute URL. An absolute URL contains all of the information necessary to reach the resource in question. You can also create URL objects from a relative URL address.

Creating a URL Relative to Another

A relative URL contains only enough information to reach the resource relative to (or in the context of) another URL.

Relative URL specifications are often used within HTML files. For example, suppose you write an HTML file called JoesHomePage.html . Within this page, are links to other pages, PicturesOfMe.html and MyKids.html , that are on the same machine and in the same directory as JoesHomePage.html . The links to PicturesOfMe.html and MyKids.html from JoesHomePage.html could be specified just as file names, like this:

These URL addresses are relative URLs. That is, the URLs are specified relative to the file in which they are contained — JoesHomePage.html .

In your Java programs, you can create a URL object from a relative URL specification. For example, suppose you know two URLs at the site example.com :

http://example.com/pages/page1.html http://example.com/pages/page2.html

You can create URL objects for these pages relative to their common base URL: http://example.com/pages/ like this:

URL myURL = new URL("http://example.com/pages/"); URL page1URL = new URL(myURL, "page1.html"); URL page2URL = new URL(myURL, "page2.html");

This code snippet uses the URL constructor that lets you create a URL object from another URL object (the base) and a relative URL specification. The general form of this constructor is:

URL(URL baseURL, String relativeURL)

The first argument is a URL object that specifies the base of the new URL . The second argument is a String that specifies the rest of the resource name relative to the base. If baseURL is null, then this constructor treats relativeURL like an absolute URL specification. Conversely, if relativeURL is an absolute URL specification, then the constructor ignores baseURL .

This constructor is also useful for creating URL objects for named anchors (also called references) within a file. For example, suppose the page1.html file has a named anchor called BOTTOM at the bottom of the file. You can use the relative URL constructor to create a URL object for it like this:

URL page1BottomURL = new URL(page1URL,"#BOTTOM");

Other URL Constructors

The URL class provides two additional constructors for creating a URL object. These constructors are useful when you are working with URLs, such as HTTP URLs, that have host name, filename, port number, and reference components in the resource name portion of the URL. These two constructors are useful when you do not have a String containing the complete URL specification, but you do know various components of the URL.

For example, suppose you design a network browsing panel similar to a file browsing panel that allows users to choose the protocol, host name, port number, and filename. You can construct a URL from the panel’s components. The first constructor creates a URL object from a protocol, host name, and filename. The following code snippet creates a URL to the page1.html file at the example.com site:

new URL("http", "example.com", "/pages/page1.html");
new URL("http://example.com/pages/page1.html");

The first argument is the protocol, the second is the host name, and the last is the pathname of the file. Note that the filename contains a forward slash at the beginning. This indicates that the filename is specified from the root of the host.

The final URL constructor adds the port number to the list of arguments used in the previous constructor:

URL gamelan = new URL("http", "example.com", 80, "pages/page1.html");

This creates a URL object for the following URL:

http://example.com:80/pages/page1.html

If you construct a URL object using one of these constructors, you can get a String containing the complete URL address by using the URL object’s toString method or the equivalent toExternalForm method.

URL addresses with Special characters

Some URL addresses contain special characters, for example the space character. Like this:

http://example.com/hello world/

To make these characters legal they need to be encoded before passing them to the URL constructor.

URL url = new URL("http://example.com/hello%20world");

Encoding the special character(s) in this example is easy as there is only one character that needs encoding, but for URL addresses that have several of these characters or if you are unsure when writing your code what URL addresses you will need to access, you can use the multi-argument constructors of the java.net.URI class to automatically take care of the encoding for you.

URI uri = new URI("http", "example.com", "/hello world/", "");

And then convert the URI to a URL.

MalformedURLException

Each of the four URL constructors throws a MalformedURLException if the arguments to the constructor refer to a null or unknown protocol. Typically, you want to catch and handle this exception by embedding your URL constructor statements in a try / catch pair, like this:

try < URL myURL = new URL(. ); >catch (MalformedURLException e) < // exception handler code here // . >

See Exceptions for information about handling exceptions.

URL s are «write-once» objects. Once you’ve created a URL object, you cannot change any of its attributes (protocol, host name, filename, or port number).

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Передача сложных объектов в параметрах URL

Представьте, что вы хотите передать примитивные типы данных, сложные объекты Java, такие как
java.util.Data, java.lang.List, универсальные классы, массивы и все, что вы хотите через параметры URL для того, чтобы предварительно установить значения по умолчанию на любой веб-странице после загрузки страницы. Общая задача? Да, но доступные решения в основном ограничены кодированием / декодированием java.lang.String. Подход, который я покажу, не имеет ограничений на типы данных. Ограничением размера URL является только одно ограничение. URL-адреса длиной более 2083 символов могут работать некорректно в старых версиях IE. Современные Firefox, Opera и Safari могут обрабатывать не менее 80000 символов в URL.

Передача объектов любого типа через параметры URL возможна, если мы сериализуем объекты в JSON и десериализуем их на стороне сервера. Закодированная строка JSON имеет действительный

формат и это путь! Хорошо, но есть проблема. Сериализация / десериализация в / из формата JSON работает нормально, если объект не является универсальным типом. Однако если объект имеет универсальный тип, то информация об универсальном типе теряется из-за стирания Java-типа. Что делать в этом случае? Решение, которое я хочу продемонстрировать, не ограничивается JSF, но, поскольку я разрабатываю внешние интерфейсы Java / Web, я вращаюсь в этом круге… Итак, начнем. Во-первых, нам нужен правильный конвертер для получения параметров URL в формате JSON и их конвертации обратно в Java.
PrimeFaces Extensions предоставляет один – JsonConverter.java. Как это работает? В следующем примере показано, как JsonConverter можно применить к f: viewParam для преобразования списка строк в формате JSON в список в Java.

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