我正在使用这个问题的例子:java.net.URI resolve against only query string,我将在这里复制:
我正在使用JDK java.net.URI来构建URI.
我想附加到一个绝对的URI对象,一个查询(在String中).例如:
- URI base = new URI("http://example.com/something/more/long");
- String queryString = "query=http://local:282/rand&action=aaaa";
- URI query = new URI(null,null,queryString,null);
- URI result = base.resolve(query);
理论(或我认为的)是这样的决心应该返回:
- http://example.com/something/more/long?query=http://local:282/rand&action=aaaa
但是我得到的是:
- http://example.com/something/more/?query=http://local:282/rand&action=aaaa
我对RFC 3986 section 5.2.2的理解是,如果相对URI的路径为空,则使用基本URI的整个路径:
- if (R.path == "") then
- T.path = Base.path;
- if defined(R.query) then
- T.query = R.query;
- else
- T.query = Base.query;
- endif;
并且只有指定路径是要与基本路径合并的相对路径:
- else
- if (R.path starts-with "/") then
- T.path = remove_dot_segments(R.path);
- else
- T.path = merge(Base.path,R.path);
- T.path = remove_dot_segments(T.path);
- endif;
- T.query = R.query;
- endif;
但Java实现始终执行合并,即使路径为空:
- String cp = (child.path == null) ? "" : child.path;
- if ((cp.length() > 0) && (cp.charAt(0) == '/')) {
- // 5.2 (5): Child path is absolute
- ru.path = child.path;
- } else {
- // 5.2 (6): Resolve relative path
- ru.path = resolvePath(base.path,cp,base.isAbsolute());
- }
如果我的阅读是正确的,要从RFC伪代码获取此行为,您可以在查询字符串之前将一个点作为相对URI中的路径,从我使用相对URI作为网页链接的经验来看,是我期望的:
- transform(Base="http://example.com/something/more/long",R=".?query")
- => T="http://example.com/something/more/?query"
但是我会期望在一个网页上,页面“http://example.com/something/more/long”到“查询”的链接将转到“http://example.com/something/more/long?query”,而不是“http://example.com/something/more/?query” – 换句话说,与RFC一致,但不是与Java实现.
我的阅读RFC是否正确,Java方法与它不一致,还是我错过了什么?
解决方法
如Raedwald所解释的(在现在删除的答案中),以/结尾或不以/结尾的基本路径有区别:
> fizz相对于/ foo / bar是:/ foo / fizz
> fizz相对于/ foo / bar /是:/ foo / bar / fizz
虽然正确,但这不是一个完整的答案,因为原来的问题不是询问一个path(即上面的“fizz”).相反,该问题涉及相对URI引用的单独的query component. URI类constructor used in the example code接受五个不同的String参数,除了queryString参数之外的所有参数都被传递为空. (请注意,Java接受一个空字符串作为路径参数,这在逻辑上会导致一个“空”路径组件,因为“the path component is never undefined”虽然它是“may be empty (zero length)”.)这将在以后很重要.
在earlier comment年,Sajan Chandran指出,java.net.URI
class被记录为实现RFC 2396,而不是RFC 3986的问题.前者在2005年被后者废弃了.URI类Javadoc没有提到新的RFC可以被解释作为其不兼容的更多证据.我们再多一点:
> JDK-6791060是一个开放的问题,建议这个类“应该更新为RFC 3986”.那里的一个评论警告说,“RFC3986并没有完全倒退
兼容2396“.
>以前尝试将URI类的部分更新为符合RFC 3986(例如JDK-6348622),但是后来的兼容性为rolled back. (另见JDK邮件列表中的this discussion)
>尽管路径“合并”逻辑听起来相似,如noted by SubOptimal所示,较新的RFC中指定的伪代码与actual implementation不匹配.在伪代码中,当相对URI的路径为空时,生成的目标路径按原样复制基本URI.在这些条件下不执行“合并”逻辑.与该规范相反,Java的URI实现修剪了最后一个字符之后的基本路径,如问题所述.
如果您想要RFC 3986行为,则可以使用URI类的替代方法. Java EE 6实现提供javax.ws.rs.core.UriBuilder
,(在泽西1.18)似乎按照预期的行为(见下文).至少就RFC的编码而言,就编码不同URI组件而言至关重要.
在J2EE之外,Spring 3.0引入了UriUtils,具体记录了“基于RFC 3986的编码和解码”. Spring 3.1不推荐使用其中的一些功能,并引入了UriComponentsBuilder,但是它不符合任何特定的RFC,不幸的是.
测试程序,展示不同的行为:
- import java.net.*;
- import java.util.*;
- import java.util.function.*;
- import javax.ws.rs.core.UriBuilder; // using Jersey 1.18
- public class StackOverflow22203111 {
- private URI withResolveURI(URI base,String targetQuery) {
- URI reference = queryOnlyURI(targetQuery);
- return base.resolve(reference);
- }
- private URI withUriBuilderReplaceQuery(URI base,String targetQuery) {
- UriBuilder builder = UriBuilder.fromUri(base);
- return builder.replaceQuery(targetQuery).build();
- }
- private URI withUriBuilderMergeURI(URI base,String targetQuery) {
- URI reference = queryOnlyURI(targetQuery);
- UriBuilder builder = UriBuilder.fromUri(base);
- return builder.uri(reference).build();
- }
- public static void main(String... args) throws Exception {
- final URI base = new URI("http://example.com/something/more/long");
- final String queryString = "query=http://local:282/rand&action=aaaa";
- final String expected =
- "http://example.com/something/more/long?query=http://local:282/rand&action=aaaa";
- StackOverflow22203111 test = new StackOverflow22203111();
- Map<String,BiFunction<URI,String,URI>> strategies = new LinkedHashMap<>();
- strategies.put("URI.resolve(URI)",test::withResolveURI);
- strategies.put("UriBuilder.replaceQuery(String)",test::withUriBuilderReplaceQuery);
- strategies.put("UriBuilder.uri(URI)",test::withUriBuilderMergeURI);
- strategies.forEach((name,method) -> {
- System.out.println(name);
- URI result = method.apply(base,queryString);
- if (expected.equals(result.toString())) {
- System.out.println(" MATCHES: " + result);
- }
- else {
- System.out.println(" EXPECTED: " + expected);
- System.out.println(" but WAS: " + result);
- }
- });
- }
- private URI queryOnlyURI(String queryString)
- {
- try {
- String scheme = null;
- String authority = null;
- String path = null;
- String fragment = null;
- return new URI(scheme,authority,path,fragment);
- }
- catch (URISyntaxException SyntaxError) {
- throw new IllegalStateException("unexpected",SyntaxError);
- }
- }
- }
输出:
- URI.resolve(URI)
- EXPECTED: http://example.com/something/more/long?query=http://local:282/rand&action=aaaa
- but WAS: http://example.com/something/more/?query=http://local:282/rand&action=aaaa
- UriBuilder.replaceQuery(String)
- MATCHES: http://example.com/something/more/long?query=http://local:282/rand&action=aaaa
- UriBuilder.uri(URI)
- MATCHES: http://example.com/something/more/long?query=http://local:282/rand&action=aaaa