#217 - Improve UriTempalte's handling of TemplateVariables.

TempalteVariables now concatenates all request parameter styles correctly. UriTemplate uses continued style of request parameters if the base URI already contains request parameters.

src/main/java/org/springframework/hateoas/TemplateVariable.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.hateoas;
 
+import static org.springframework.hateoas.TemplateVariable.VariableType.*;
+
 import java.io.Serializable;
 import java.util.Arrays;
 import java.util.List;
@@ -119,6 +121,35 @@ public final class TemplateVariable implements Serializable {
 		return this.type.canBeCombinedWith(variable.type);
 	}
 
+	/**
+	 * Returns whether the given {@link TemplateVariable} is logically equivalent to the given one. This considers request
+	 * parameter variables equivalent independently from whether they're continued or not.
+	 * 
+	 * @param variable
+	 * @return
+	 */
+	boolean isEquivalent(TemplateVariable variable) {
+		return this.name.equals(variable.name) && isCombinable(variable);
+	}
+
+	/**
+	 * Returns whether the current {@link TemplateVariable} is representing a request parameter.
+	 * 
+	 * @return
+	 */
+	boolean isRequestParameterVariable() {
+		return type.equals(REQUEST_PARAM) || type.equals(REQUEST_PARAM_CONTINUED);
+	}
+
+	/**
+	 * Returns whether the variable is a fragement one.
+	 * 
+	 * @return
+	 */
+	boolean isFragment() {
+		return type.equals(FRAGMENT);
+	}
+
 	/* 
 	 * (non-Javadoc)
 	 * @see java.lang.Object#toString()

src/main/java/org/springframework/hateoas/TemplateVariables.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.hateoas;
 
+import static org.springframework.hateoas.TemplateVariable.VariableType.*;
+
 import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -23,6 +25,7 @@ import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 
+import org.springframework.hateoas.TemplateVariable.VariableType;
 import org.springframework.util.Assert;
 
 /**
@@ -79,7 +82,7 @@ public final class TemplateVariables implements Iterable<TemplateVariable>, Seri
 		result.addAll(this.variables);
 
 		for (TemplateVariable variable : variables) {
-			if (!result.contains(variable)) {
+			if (!containsEquivalentFor(variable)) {
 				result.add(variable);
 			}
 		}
@@ -106,6 +109,17 @@ public final class TemplateVariables implements Iterable<TemplateVariable>, Seri
 		return this.variables;
 	}
 
+	private boolean containsEquivalentFor(TemplateVariable candidate) {
+
+		for (TemplateVariable variable : this.variables) {
+			if (variable.isEquivalent(candidate)) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+
 	/* 
 	 * (non-Javadoc)
 	 * @see java.lang.Iterable#iterator()
@@ -121,6 +135,16 @@ public final class TemplateVariables implements Iterable<TemplateVariable>, Seri
 	 */
 	@Override
 	public String toString() {
+		return toString(false);
+	}
+
+	/**
+	 * Returns the string representation of the template but forcing a continued style of expressing request parameters.
+	 * 
+	 * @param appended
+	 * @return
+	 */
+	String toString(boolean appended) {
 
 		if (variables.isEmpty()) {
 			return "";
@@ -131,10 +155,13 @@ public final class TemplateVariables implements Iterable<TemplateVariable>, Seri
 
 		for (TemplateVariable variable : variables) {
 
+			VariableType type = variable.getType();
+			type = appended && type.equals(REQUEST_PARAM) ? REQUEST_PARAM_CONTINUED : type;
+
 			if (previous == null) {
-				builder.append("{").append(variable.getType().toString());
+				builder.append("{").append(type.toString());
 			} else if (!previous.isCombinable(variable)) {
-				builder.append("}{").append(variable.getType().toString());
+				builder.append("}{").append(type.toString());
 			} else {
 				builder.append(",");
 			}

src/main/java/org/springframework/hateoas/UriTemplate.java

@@ -28,6 +28,7 @@ import java.util.regex.Pattern;
 import org.springframework.hateoas.TemplateVariable.VariableType;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
+import org.springframework.web.util.UriComponents;
 import org.springframework.web.util.UriComponentsBuilder;
 
 /**
@@ -106,7 +107,26 @@ public class UriTemplate implements Iterable<TemplateVariable>, Serializable {
 			return this;
 		}
 
-		return new UriTemplate(baseUri, this.variables.concat(variables));
+		UriComponents components = UriComponentsBuilder.fromUriString(baseUri).build();
+		List<TemplateVariable> result = new ArrayList<TemplateVariable>();
+
+		for (TemplateVariable variable : variables) {
+
+			boolean isRequestParam = variable.isRequestParameterVariable();
+			boolean alreadyPresent = components.getQueryParams().containsKey(variable.getName());
+
+			if (isRequestParam && alreadyPresent) {
+				continue;
+			}
+
+			if (variable.isFragment() && StringUtils.hasText(components.getFragment())) {
+				continue;
+			}
+
+			result.add(variable);
+		}
+
+		return new UriTemplate(baseUri, this.variables.concat(result));
 	}
 
 	/**
@@ -212,7 +232,11 @@ public class UriTemplate implements Iterable<TemplateVariable>, Serializable {
 	 */
 	@Override
 	public String toString() {
-		return baseUri + getOptionalVariables().toString();
+
+		UriComponents components = UriComponentsBuilder.fromUriString(baseUri).build();
+		boolean hasQueryParameters = !components.getQueryParams().isEmpty();
+
+		return baseUri + getOptionalVariables().toString(hasQueryParameters);
 	}
 
 	private TemplateVariables getOptionalVariables() {