in fact Java 1.5 should support enum in annotations if the enum is defined before the field declaration

sonar-plugin-api/src/main/java/org/sonar/api/rules/Rule.java

@@ -24,7 +24,6 @@ import org.apache.commons.lang.builder.EqualsBuilder;
 import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.apache.commons.lang.builder.ToStringBuilder;
 import org.sonar.api.database.DatabaseProperties;
-import org.sonar.check.Cardinality;
 
 import javax.persistence.*;
 import java.util.ArrayList;
@@ -72,7 +71,7 @@ public final class Rule {
 
   @Enumerated(EnumType.STRING)
   @Column(name = "cardinality", updatable = true, nullable = false)
-  private Cardinality cardinality = Cardinality.SINGLE;
+  private org.sonar.check.Rule.Cardinality cardinality = org.sonar.check.Rule.Cardinality.SINGLE;
 
   @ManyToOne(fetch = FetchType.EAGER)
   @JoinColumn(name = "parent_id", updatable = true, nullable = true)
@@ -332,11 +331,11 @@ public final class Rule {
     return setRepositoryKey(repositoryKey).setKey(key).setConfigKey(key);
   }
 
-  public Cardinality getCardinality() {
+  public org.sonar.check.Rule.Cardinality getCardinality() {
     return cardinality;
   }
 
-  public Rule setCardinality(Cardinality c) {
+  public Rule setCardinality(org.sonar.check.Rule.Cardinality c) {
     this.cardinality = c;
     return this;
   }

sonar-plugin-api/src/main/java/org/sonar/api/rules/XMLRuleParser.java

@@ -139,7 +139,7 @@ public final class XMLRuleParser implements ServerComponent {
         rule.setRulesCategory(new RulesCategory(category));
 
       } else if (StringUtils.equalsIgnoreCase("cardinality", nodeName)) {
-        rule.setCardinality(org.sonar.check.Cardinality.valueOf(StringUtils.trim(cursor.collectDescendantText(false))));
+        rule.setCardinality(org.sonar.check.Rule.Cardinality.valueOf(StringUtils.trim(cursor.collectDescendantText(false))));
 
       } else if (StringUtils.equalsIgnoreCase("param", nodeName)) {
         processParameter(rule, cursor);

sonar-plugin-api/src/test/java/org/sonar/api/rules/XMLRuleParserTest.java

@@ -22,7 +22,7 @@ package org.sonar.api.rules;
 import org.hamcrest.core.Is;
 import org.junit.Test;
 import org.sonar.api.utils.SonarException;
-import org.sonar.check.Cardinality;
+import org.sonar.check.Rule.Cardinality;
 
 import java.io.StringReader;
 import java.util.List;