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I am trying to call a URL from Java code in the following way:

userId = "Ankur";
template = "HelloAnkur";
value= "ParamValue";
String urlString = "https://graph.facebook.com/" + userId + "/notifications?template=" +
    template + "&href=processThis.jsp?param=" + value + "&access_token=abc123";

I have the following problems in this:

  1. When I do println(urlString), I see that the urlString only has the value upto and before the first ampersand (&). That is, it looks as: https://graph.facebook.com/Ankur/notifications?template=HelloAnkur and rest of it all (which should have been &href=processThis.jsp?param=ParamValue&access_toke=abc123) gets cut off. Why is that and how can I get and keep the full value in urlString? Does & needs to be escaped in a Java String, and if yes, how to do it?
  2. Notice that I am trying to pass a (relative) URL as a parameter value in this query (the value of href as processThis.jsp?param=ParamValue. How can I pass this type of value of href without mixing it up with the query of this URL (urlString), which only has three parameters template, href and access_token? That is, how can I hide or escape ? and =? Further, what would I need to do if value was Param Value (with a space)?
  3. Notice that the template has the value HelloAnkur (with no space). But if I wanted it to have space, as in Hello Ankur, how would I do it? Should I write it as Hello%20Ankur or Hello Ankur would be fine?
  4. I need the solution in such a way that URL url = new URL(urlString) can be created, or url can be created via URI. Please describe your answer up to this point as creating a safe URL is not straight forward in Java.

Thanks!

share|improve this question
    
I don't use Java, but there's this link that talks about URLEncoding in Java, which is what you need for your URI I think: stackoverflow.com/questions/10786042/java-url-encoding –  dKen Jun 6 '13 at 16:21
    
@dKen I tried this, it did not work for me. My first problem here is that the URL String gets truncated at the first &, and I don't know why. Your reference talks about encoding the query parameters' values. That is my later problem. –  Ankur Jun 6 '13 at 19:53

1 Answer 1

up vote 1 down vote accepted

(this is going to become a classic)

Use URI Templates (RFC 6570). Using this implementation (disclaimer: mine), you can avoid all encoding problems altogether:

// Immutable, can be reused as many times as you wish
final URITemplate template = new URITemplate("https://graph.facebook.com/{userId}"
    + "/notifications?template={template}"
    + "&href=processThis.jsp?param={value}"
    + "&access_token=abc123");

final Map<String, VariableValue> vars = new HashMap<String, VariableValue>();

vars.put("userId", new ScalarValue("Ankur"));
vars.put("template", new ScalarValue("HelloAnkur"));
vars.put("value", new ScalarValue("ParamValue");

// Build the expanded string
final String expanded = template.expand(vars);

// Go with the string

Note that URI templates not only allow scalar values, but also arrays (the RFC calls these "lists" -- implemented as ListValue in the above) and maps (the RFC calls these "associative arrays" -- implemented as MapValue in the above).

share|improve this answer
    
How can I use your implementation -- will I have to import a package so that URITemplate can be recognized? Will I have to download something or can I copy-paste the code in some way in my project? BTW, I am using Eclipse and my code is deployed on Google App Engine. I would appreciate if you could provide directions. Thanks. –  Ankur Jun 6 '13 at 19:30
    
Do you use maven in your project? –  fge Jun 6 '13 at 19:31
    
I forgot: you can just download it from Maven central, see here. Note: Guava is also needed as a dependency. Other jars (testng, jackson-coreutils) are only needed for tests –  fge Jun 6 '13 at 19:34
    
No, I don't use Maven or Guava. (I don't know what it is, and how it can be used with Eclipse and Google App Engine). –  Ankur Jun 6 '13 at 19:56
    
No need for maven especially. But you'll need to download Guava. Follow the links to it in the link above. –  fge Jun 6 '13 at 19:58

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