HttpConnection Class

About the HttpConnection Class

The HttpConnection class makes a HTTP connection to a given URI. You can use it to make GET and POST requests to other web services.

Considerations

• HTTPS calls are supported only for URIs that have standard security certificates.

• When you call the execute method in HttpConnection, it executes the request, gets the response, and closes the connection. This means that a single object cannot be used multiple times. For multiple HTTP requests, instantiate multiple instances.

• Make sure that the URL is properly encoded when instantiating an HttpConnection object.

Learn more:

• URL Encoding
• HowTo:Use the HttpConnection Class to access a web service

Constructor

You create an instance of HttpConnection using the new operator.

Method signature

HttpConnection con = new HttpConnection(int methodType, String encoded_URI)

methodType

Sets the HTTP method type:

• CONSTANTS.HTTP.METHOD.GET for an HTTP GET request
• CONSTANTS.HTTP.METHOD.POST for an HTTP POST request

String encoded_URI

Properly encoded URI to connect to
Learn more: URL Encoding

Methods

The methods are:

• addHeader
• addParameter
• execute
• getResponse
• encode
• getResponseHeaders
• setRequestBody

addHeader

Adds a key-value pair to the request header.

Method signature

void addHeader(String key, String value)

Parameters

• key - The name of the key
• value - The value of the key

Return

None

addParameter

Adds a parameter to an HTTP POST request. This methods throws an exception if it is called for an HTTP GET request.

Method signature

void addParameter(String key, String value)

Parameters

• key - The name of the key
• value - The value of the key

Return

None

execute

Executes the request and returns a standard HTTP response such as "200 - OK" or "404 - not found".

Method signature

int execute()

Parameters

None

Return

Standard HTTP response

getResponse

Returns the response as a String.

Method signature

String getResponse()

Parameters

None

Return

The response from the service

encode

Returns a String encoded from s.

Method signature

String encode(String s)

Parameters

• s - The string to encode

Return

The encoded string

getResponseHeaders

Retrieve the headers from the HTTP Response from an external server. It is a map of String Header Name/Header Value pairs.

For example, if the Header Content-Length is equal to 10008, then "Content-Length" is the Header Name and "10008" is the Header Value.

This method is to be called after execute method of HttpConnection.

Method signature

HashMap<String name, String value> getResponseHeaders()

Parameters

None

Return

A HashMap of Header Name/Header Value string pairs

setRequestBody

Specify the body of the request, the content type, and character set.

Method signature

HashMap<String name, String value> getResponseHeaders()

Parameters

• content-Type - String. One of the valid MIME types for the body of a request. For example: "application/xml".
• charSet - String. The character set used in the request. For example: "utf-8".

Return

None

Learn more:

• MIME types
• CharSets

HttpConnection Example

This example gets the result of a Google search for "IT Leaders".

<syntaxhighlight lang="java" enclose="div"> HttpConnection con = new HttpConnection(CONSTANTS.HTTP.METHOD.GET, "http://www.google.com/search?hl=en&q=IT+Leaders&btnG=Google+Search"); int code= con.execute(); String response = con.getResponse(); </syntaxhighlight >

Note: The typical response format is JSON. Those libraries are built into the platform. The APIs are documented at JSON.org.