将相对URL附加到java.net.URL

Question

如果我有一个java.net.URL对象,指向让我们说

http://example.com/myItems 要么 http://example.com/myItems/

是否有某个帮助器在某处附加一些相对URL？例如追加./myItemId或myItemId得到: http://example.com/myItems/myItemId

Answer 1

URL有一个带基数和规格的构造函数.URLString

或者,java.net.URI更贴近标准,并有一个resolve方法来做同样的事情.URI从您的URL使用中创建一个URL.toURI.

Answer 2

这个不需要任何额外的库或代码,并给出了所需的结果:

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);

这打印:

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

只有在主机之后没有路径(恕我直言,接受的答案是错误的)时,接受的答案才有效

Answer 3

您只需使用URI该类即可：

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

请注意基本路径上的尾部斜杠以及要附加的段的基本相对格式。您还可以使用URIBuilderApache HTTP 客户端中的类：

<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();
}

Answer 4

我不敢相信URI.resolve()它充满了令人讨厌的边缘情况，真的是多么令人讨厌。

new URI("http://localhost:80").resolve("foo") => "http://localhost:80foo"
new URI("http://localhost:80").resolve("//foo") => "http://foo"
new URI("http://localhost:80").resolve(".//foo") => "http://foo"

我见过的以可预测的方式处理这些边缘情况的最简洁的解决方案是：

URI addPath(URI uri, String path) {
    String newPath;
    if (path.startsWith("/")) newPath = path.replaceAll("//+", "/");
    else if (uri.getPath().endsWith("/")) newPath = uri.getPath() + path.replaceAll("//+", "/");
    else newPath = uri.getPath() + "/" + path.replaceAll("//+", "/");

    return uri.resolve(newPath).normalize();
}

结果：

jshell> addPath(new URI("http://localhost"), "sub/path")
$3 ==> http://localhost/sub/path

jshell> addPath(new URI("http://localhost/"), "sub/path")
$4 ==> http://localhost/sub/path

jshell> addPath(new URI("http://localhost/"), "/sub/path")
$5 ==> http://localhost/sub/path

jshell> addPath(new URI("http://localhost/random-path"), "/sub/path")
$6 ==> http://localhost/sub/path

jshell> addPath(new URI("http://localhost/random-path"), "./sub/path")
$7 ==> http://localhost/random-path/sub/path

jshell> addPath(new URI("http://localhost/random-path"), "../sub/path")
$8 ==> http://localhost/sub/path

jshell> addPath(new URI("http://localhost"), "../sub/path")
$9 ==> http://localhost/../sub/path

jshell> addPath(new URI("http://localhost/"), "//sub/path")
$10 ==> http://localhost/sub/path

jshell> addPath(new URI("http://localhost/"), "//sub/./path")
$11 ==> http://localhost/sub/path

Answer 5

您可以使用URIBuilder和方法来避免URI 中的URI#normalize重复：/

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

Answer 6

这是我写的一个辅助函数,用于添加到url路径:

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();
}