Package com.google.api.pathtemplate

Class PathTemplate

  • public class PathTemplate
extends Object
    Represents a path template.

    Templates use the syntax of the API platform; see the protobuf of HttpRule for details. A template consists of a sequence of literals, wildcards, and variable bindings, where each binding can have a sub-path. A string representation can be parsed into an instance of PathTemplate, which can then be used to perform matching and instantiation.

    Matching and instantiation deals with unescaping and escaping using URL encoding rules. For example, if a template variable for a single segment is instantiated with a string like "a/b", the slash will be escaped to "%2f". (Note that slash will not be escaped for a multiple-segment variable, but other characters will). The literals in the template itself are not escaped automatically, and must be already URL encoded.

    Here is an example for a template using simple variables: 

    
 PathTemplate template = PathTemplate.create("v1/shelves/{shelf}/books/{book}");
 assert template.matches("v2/shelves") == false;
 Map<String, String> values = template.match("v1/shelves/s1/books/b1");
 Map<String, String> expectedValues = new HashMap<>();
 expectedValues.put("shelf", "s1");
 expectedValues.put("book", "b1");
 assert values.equals(expectedValues);
 assert template.instantiate(values).equals("v1/shelves/s1/books/b1");
    Templates can use variables which match sub-paths. Example: 
    
 PathTemplate template = PathTemplate.create("v1/{name=shelves/*/books/*}";
 assert template.match("v1/shelves/books/b1") == null;
 Map<String, String> expectedValues = new HashMap<>();
 expectedValues.put("name", "shelves/s1/books/b1");
 assert template.match("v1/shelves/s1/books/b1").equals(expectedValues);
 }
    Path templates can also be used with only wildcards. Each wildcard is associated with an implicit variable $n, where n is the zero-based position of the wildcard. Example: 
    
 PathTemplate template = PathTemplate.create("shelves/*&#47;books/*";
 assert template.match("shelves/books/b1") == null;
 Map<String, String> values = template.match("v1/shelves/s1/books/b1");
 Map<String, String> expectedValues = new HashMap<>();
 expectedValues.put("$0", s1");
 expectedValues.put("$1", "b1");
 assert values.equals(expectedValues);
 }
    Paths input to matching can use URL relative syntax to indicate a host name by prefixing the host name, as in //somewhere.io/some/path. The host name is matched into the special variable HOSTNAME_VAR. Patterns are agnostic about host names, and the same pattern can be used for URL relative syntax and simple path syntax: 
    
 PathTemplate template = PathTemplate.create("shelves/*";
 Map<String, String> expectedValues = new HashMap<>();
 expectedValues.put(PathTemplate.HOSTNAME_VAR, "//somewhere.io");
 expectedValues.put("$0", s1");
 assert template.match("//somewhere.io/shelves/s1").equals(expectedValues);
 expectedValues.clear();
 expectedValues.put("$0", s1");
 assert template.match("shelves/s1").equals(expectedValues);
 }
    For the representation of a resource name see TemplatedResourceName, which is based on path templates.

    • Field Detail

      • HOSTNAME_VAR

        public static final String HOSTNAME_VAR
        A constant identifying the special variable used for endpoint bindings in the result of matchFromFullName(String). It may also contain protocol string, if its provided in the input.
        See Also:
        Constant Field Values

    • Method Detail

      • create

        public static PathTemplate create​(String template)
        Creates a path template from a string. The string must satisfy the syntax of path templates of the API platform; see HttpRule's proto source.
        Throws:
        ValidationException - if there are errors while parsing the template.

      • createWithoutUrlEncoding

        public static PathTemplate createWithoutUrlEncoding​(String template)
        Creates a path template from a string. The string must satisfy the syntax of path templates of the API platform; see HttpRule's proto source. Url encoding of template variables is disabled.
        Throws:
        ValidationException - if there are errors while parsing the template.

      • vars

        public Set<String> vars()
        Returns the set of variable names used in the template.

      • parentTemplate

        public PathTemplate parentTemplate()
        Returns a template for the parent of this template.
        Throws:
        ValidationException - if the template has no parent.

      • withoutVars

        public PathTemplate withoutVars()
        Returns a template where all variable bindings have been replaced by wildcards, but which is equivalent regards matching to this one.

      • subTemplate

        public PathTemplate subTemplate​(String varName)
        Returns a path template for the sub-path of the given variable. Example: 
        
 PathTemplate template = PathTemplate.create("v1/{name=shelves/*&#47;books/*}");
 assert template.subTemplate("name").toString().equals("shelves/*&#47;books/*");
        The returned template will never have named variables, but only wildcards, which are dealt with in matching and instantiation using '$n'-variables. See the documentation of match(String) and instantiate(Map), respectively.

        For a variable which has no sub-path, this returns a path template with a single wildcard ('*').

        Throws:
        ValidationException - if the variable does not exist in the template.

      • endsWithLiteral

        public boolean endsWithLiteral()
        Returns true of this template ends with a literal.

      • endsWithCustomVerb

        public boolean endsWithCustomVerb()
        Returns true of this template ends with a custom verb.

      • singleVar

        @Nullable
public String singleVar()
        Returns the name of a singleton variable used by this template. If the template does not contain a single variable, returns null.

      • validate

        public void validate​(String path,
                     String exceptionMessagePrefix)
        Throws a ValidationException if the template doesn't match the path. The exceptionMessagePrefix parameter will be prepended to the ValidationException message.

      • validatedMatch

        public Map<String,​String> validatedMatch​(String path,
                                               String exceptionMessagePrefix)
        Matches the path, returning a map from variable names to matched values. All matched values will be properly unescaped using URL encoding rules. If the path does not match the template, throws a ValidationException. The exceptionMessagePrefix parameter will be prepended to the ValidationException message.

        If the path starts with '//', the first segment will be interpreted as a host name and stored in the variable HOSTNAME_VAR.

        See the PathTemplate class documentation for examples.

        For free wildcards in the template, the matching process creates variables named '$n', where 'n' is the wildcard's position in the template (starting at n=0). For example: 

        
 PathTemplate template = PathTemplate.create("shelves/*&#47;books/*");
 Map&lt;String, String&gt; expectedValues = new HashMap&lt;&gt;();
 expectedValues.put("$0", "s1");
 expectedValues.put("$1", "b1");
 assert template.validatedMatch("shelves/s1/books/b2", "User exception string")
            .equals(expectedValues);
 expectedValues.clear();
 expectedValues.put(HOSTNAME_VAR, "//somewhere.io");
 expectedValues.put("$0", "s1");
 expectedValues.put("$1", "b1");
 assert template.validatedMatch("//somewhere.io/shelves/s1/books/b2", "User exception string")
            .equals(expectedValues);
        All matched values will be properly unescaped using URL encoding rules (so long as URL encoding has not been disabled by the createWithoutUrlEncoding(java.lang.String) method).

      • matches

        public boolean matches​(String path)
        Returns true if the template matches the path.

      • match

        @Nullable
public Map<String,​String> match​(String path)
        Matches the path, returning a map from variable names to matched values. All matched values will be properly unescaped using URL encoding rules. If the path does not match the template, null is returned.

        If the path starts with '//', the first segment will be interpreted as a host name and stored in the variable HOSTNAME_VAR.

        See the PathTemplate class documentation for examples.

        For free wildcards in the template, the matching process creates variables named '$n', where 'n' is the wildcard's position in the template (starting at n=0). For example: 

        
 PathTemplate template = PathTemplate.create("shelves/*&#47;books/*");
 Map&lt;String, String&gt; expectedValues = new HashMap&lt;&gt;();
 expectedValues.put("$0", "s1");
 expectedValues.put("$1", "b1");
 assert template.match("shelves/s1/books/b2").equals(expectedValues);
 expectedValues.clear();
 expectedValues.put(HOSTNAME_VAR, "//somewhere.io");
 expectedValues.put("$0", "s1");
 expectedValues.put("$1", "b1");
 assert template.match("//somewhere.io/shelves/s1/books/b2").equals(expectedValues);
        All matched values will be properly unescaped using URL encoding rules (so long as URL encoding has not been disabled by the createWithoutUrlEncoding(java.lang.String) method).

      • matchFromFullName

        @Nullable
public Map<String,​String> matchFromFullName​(String path)
        Matches the path, where the first segment is interpreted as the host name regardless of whether it starts with '//' or not. Example: 
        
 Map&lt;String, String&gt; expectedValues = new HashMap&lt;&gt;();
 expectedValues.put(HOSTNAME_VAR, "//somewhere.io");
 expectedValues.put("name", "shelves/s1");
 assert template("{name=shelves/*}").matchFromFullName("somewhere.io/shelves/s1")
          .equals(expectedValues);

      • instantiate

        public String instantiate​(Map<String,​String> values)
        Instantiate the template based on the given variable assignment. Performs proper URL escaping of variable assignments.

        Note that free wildcards in the template must have bindings of '$n' variables, where 'n' is the position of the wildcard (starting at 0). See the documentation of match(String) for details.

        Throws:
        ValidationException - if a variable occurs in the template without a binding.

      • instantiate

        public String instantiate​(String... keysAndValues)
        Shortcut for instantiate(Map) with a vararg parameter for keys and values.

      • instantiatePartial

        public String instantiatePartial​(Map<String,​String> values)
        Same like instantiate(Map) but allows for unbound variables, which are substituted using their original syntax. Example: 
        
 PathTemplate template = PathTemplate.create("v1/shelves/{shelf}/books/{book}");
 Map&lt;String, String&gt; partialMap = new HashMap&lt;&gt;();
 partialMap.put("shelf", "s1");
 assert template.instantiatePartial(partialMap).equals("v1/shelves/s1/books/{book}");
        The result of this call can be used to create a new template.

      • encode

        public String encode​(String... values)
        Instantiates the template from the given positional parameters. The template must not be build from named bindings, but only contain wildcards. Each parameter position corresponds to a wildcard of the according position in the template.

      • decode

        public List<String> decode​(String path)
        Matches the template into a list of positional values. The template must not be build from named bindings, but only contain wildcards. For each wildcard in the template, a value is returned at corresponding position in the list.

      • toString

        public String toString()
        Returns a pretty version of the template as a string.
        Overrides:
        toString in class Object

      • toRawString

        public String toRawString()
        Returns a raw version of the template as a string. This renders the template in its internal, normalized form.

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class Object