Append relative URL to java.net.URL

问题:

Provided I have a java.net.URL object, pointing to let's say

http://example.com/myItems or http://example.com/myItems/

Is there some helper somewhere to append some relative URL to this? For instance append ./myItemId or myItemId to get : http://example.com/myItems/myItemId

回答1:

URL has a constructor that takes a base URL and a String spec.

Alternatively, java.net.URI adheres more closely to the standards, and has a resolve method to do the same thing. Create a URI from your URL using URL.toURI.

回答2:

This one does not need any extra libs or code and gives the desired result:

URL url1 = new URL("http://petstore.swagger.wordnik.com/api/api-docs");
URL url2 = new URL(url1.getProtocol(), url1.getHost(), url1.getPort(), url1.getFile() + "/pet", null);
System.out.println(url1);
System.out.println(url2);

This prints:

http://petstore.swagger.wordnik.com/api/api-docs
http://petstore.swagger.wordnik.com/api/api-docs/pet

The accepted answer only works if there is no path after the host (IMHO the accepted answer is wrong)

回答3:

Here is a helper function I've written to add to the url path:

public static URL concatenate(URL baseUrl, String extraPath) throws URISyntaxException, 
                                                                    MalformedURLException {
    URI uri = baseUrl.toURI();
    String newPath = uri.getPath() + '/' + extraPath;
    URI newUri = uri.resolve(newPath);
    return newUri.toURL();
}

回答4:

I've searched far and wide for an answer to this question. The only implementation I can find is in the Android SDK: Uri.Builder. I've extracted it for my own purposes.

private String appendSegmentToPath(String path, String segment) {
  if (path == null || path.isEmpty()) {
    return "/" + segment;
  }

  if (path.charAt(path.length() - 1) == '/') {
    return path + segment;
  }

  return path + "/" + segment;
}

This is where I found the source.

In conjunction with Apache URIBuilder, this is how I'm using it: builder.setPath(appendSegmentToPath(builder.getPath(), segment));

回答5:

You can use URIBuilder and the method URI#normalize to avoid duplicate / in the URI:

URIBuilder uriBuilder = new URIBuilder("http://example.com/test");
URI uri = uriBuilder.setPath(uriBuilder.getPath() + "/path/to/add")
          .build()
          .normalize();
// expected : http://example.com/test/path/to/add

回答6:

Some examples using the Apache URIBuilder http://hc.apache.org/httpcomponents-client-4.3.x/httpclient/apidocs/org/apache/http/client/utils/URIBuilder.html:

Ex1:

String url = "http://example.com/test";
URIBuilder builder = new URIBuilder(url);
builder.setPath((builder.getPath() + "/example").replaceAll("//+", "/"));
System.out.println("Result 1 -> " + builder.toString());

Result 1 -> http://example.com/test/example

Ex2:

String url = "http://example.com/test";
URIBuilder builder = new URIBuilder(url);
builder.setPath((builder.getPath() + "///example").replaceAll("//+", "/"));
System.out.println("Result 2 -> " + builder.toString());

Result 2 -> http://example.com/test/example

回答7:

UPDATED

I believe this is the shortest solution:

URL url1 = new URL("http://domain.com/contextpath");
String relativePath = "/additional/relative/path";
URL concatenatedUrl = new URL(url1.toExternalForm() + relativePath);

回答8:

You can just use the URI class for this:

import java.net.URI;
import org.apache.http.client.utils.URIBuilder;

URI uri = URI.create("http://example.com/basepath/");
URI uri2 = uri.resolve("./relative");
// => http://example.com/basepath/relative

Note the trailing slash on the base path and the base-relative format of the segment that's being appended. You can also use the URIBuilder class from Apache HTTP client:

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.3</version>
</dependency>

...

import java.net.URI;
import org.apache.http.client.utils.URIBuilder;

URI uri = URI.create("http://example.com/basepath");
URI uri2 = appendPath(uri, "relative");
// => http://example.com/basepath/relative

public URI appendPath(URI uri, String path) {
    URIBuilder builder = new URIBuilder(uri);
    builder.setPath(URI.create(builder.getPath() + "/").resolve("./" + path).getPath());
    return builder.build();
}

回答9:

Concatenate a relative path to a URI:

java.net.URI uri = URI.create("https://stackoverflow.com/questions")
java.net.URI res = uri.resolve(uri.getPath + "/some/path")

res will contain https://stackoverflow.com/questions/some/path

回答10:

I had some difficulty with the encoding of URI's. Appending was not working for me because it was of a content:// type and it was not liking the "/". This solution assumes no query, nor fragment(we are working with paths after all):

Kotlin code:

  val newUri = Uri.parse(myUri.toString() + Uri.encode("/$relPath"))

回答11:

My solution based on twhitbeck answer:

import java.net.URI;
import java.net.URISyntaxException;

public class URIBuilder extends org.apache.http.client.utils.URIBuilder {
    public URIBuilder() {
    }

    public URIBuilder(String string) throws URISyntaxException {
        super(string);
    }

    public URIBuilder(URI uri) {
        super(uri);
    }

    public org.apache.http.client.utils.URIBuilder addPath(String subPath) {
        if (subPath == null || subPath.isEmpty() || "/".equals(subPath)) {
            return this;
        }
        return setPath(appendSegmentToPath(getPath(), subPath));
    }

    private String appendSegmentToPath(String path, String segment) {
        if (path == null || path.isEmpty()) {
            path = "/";
        }

        if (path.charAt(path.length() - 1) == '/' || segment.startsWith("/")) {
            return path + segment;
        }

        return path + "/" + segment;
    }
}

Test:

import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class URIBuilderTest {

    @Test
    public void testAddPath() throws Exception {
        String url = "http://example.com/test";
        String expected = "http://example.com/test/example";

        URIBuilder builder = new URIBuilder(url);
        builder.addPath("/example");
        assertEquals(expected, builder.toString());

        builder = new URIBuilder(url);
        builder.addPath("example");
        assertEquals(expected, builder.toString());

        builder.addPath("");
        builder.addPath(null);
        assertEquals(expected, builder.toString());

        url = "http://example.com";
        expected = "http://example.com/example";

        builder = new URIBuilder(url);
        builder.addPath("/");
        assertEquals(url, builder.toString());
        builder.addPath("/example");
        assertEquals(expected, builder.toString());
    }
}

Gist: https://gist.github.com/enginer/230e2dc2f1d213a825d5

回答12:

For android make sure you use .appendPath() from android.net.Uri