How to build url in java?

问题:

I am building a String with StringBuilder

StringBuilder builder = new StringBuilder();
builder.append("my parameters");
builder.append("other parameters");

Then i build a Url

Url url = new Url(builder.toString());

And then i try the connection

HttpURLConnection connection = (HttpURLConnection) url.openConnection();

But the url seems not to be right from the results i get. It's like some parameter is being false passed. That's why i think the problem is in the part of the StringBuilder.

The problem is in a double parameter i try to pass.

double longitude = 23.433114;
String lng = String.ValueOf(longitude);

And then i put it in the url. But if i give it as a string the result is correct.

String lng = "23.433114"

Is UrlEncoding necessary? I will try what is suggested below.

回答1:

Try apache's URIBuilder : [Documentation]

import org.apache.http.client.utils.URIBuilder;

// ...

URIBuilder b = new URIBuilder("http://example.com");
b.addParameter("t", "search");
b.addParameter("q", "apples");

Url url = b.build().toUrl();

Maven dependency:

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.1</version>
</dependency>

回答2:

Since you want to create the URL and consume it through a GET request, it would be better to use a library that helps you in this process. You can use HttpComponents or another library like Unirest that is built on top of HttpComponents which ease all this work.

Here's an example using Unirest:

HttpResponse<String> stringResponse = Unirest.get("https://www.youtube.com/results")
    .field("search_query", "eñe")
    .asString();
System.out.println(stringResponse.getBody());

This will retrieve the HTML response corresponding to all the results from a search on youtube using "eñe". The ñ character will be encoded for you.

DISCLAIMER: I'm not attached to Unirest in any mean. I'm not a developer or a sponsor of this project. I'm only a happy user of this framework.