How to programmatically access web page in java

问题:

There is a web page from which I want to retrieve a certain string. In order to do so, I need to login, click some buttons, fill a text box, click another button - and then the string appears.

How can I write a java program to do that automatically? Are there any useful libraries for that purpose?

Thanks

回答1:

Try HtmlUnit

HtmlUnit is a "GUI-Less browser for Java programs". It models HTML documents and provides an API that allows you to invoke pages, fill out forms, click links, etc... just like you do in your "normal" browser.

Example code for submiting form:

@Test
public void submittingForm() throws Exception {
    final WebClient webClient = new WebClient();

    // Get the first page
    final HtmlPage page1 = webClient.getPage("http://some_url");

    // Get the form that we are dealing with and within that form, 
    // find the submit button and the field that we want to change.
    final HtmlForm form = page1.getFormByName("myform");

    final HtmlSubmitInput button = form.getInputByName("submitbutton");
    final HtmlTextInput textField = form.getInputByName("userid");

    // Change the value of the text field
    textField.setValueAttribute("root");

    // Now submit the form by clicking the button and get back the second page.
    final HtmlPage page2 = button.click();

    webClient.closeAllWindows();
}

For more details check: http://htmlunit.sourceforge.net/gettingStarted.html

回答2:

The super simple way to do this is using HtmlUnit here:

http://htmlunit.sourceforge.net/

and what you want to do can be as simple as:

@Test
public void homePage() throws Exception {
    final WebClient webClient = new WebClient();
    final HtmlPage page = webClient.getPage("http://htmlunit.sourceforge.net");
    assertEquals("HtmlUnit - Welcome to HtmlUnit", page.getTitleText());
}

回答3:

Take a look at the apache HttpClient project, or if you need to run Javascript on the page, try HttpUnit.

回答4:

Well when you press a button usually you do a request via a HTTP POST method, so you should use HttpClient to handle request and HtmlParser to handle the response page with the string you need.

回答5:

Yes:

• java.net.URL#openConnection() will allow you to make http requests and get the http responses

• Apache HttpComponents is a library that makes it easier to work with HTTP.