Added expectSubject convenience method.

src/main/java/io/jsonwebtoken/JwtParser.java

@@ -27,6 +27,14 @@ public interface JwtParser {
 
     public static final char SEPARATOR_CHAR = '.';
 
+    /**
+     * Sets an expected value for the subject claim.
+     *
+     * @param subject
+     * @return the parser for method chaining.
+     */
+    JwtParser expectSubject(String subject);
+
     /**
      * Sets an expected value for the audience claim.
      *

src/main/java/io/jsonwebtoken/impl/DefaultJwtParser.java

@@ -87,6 +87,13 @@ public class DefaultJwtParser implements JwtParser {
         return this;
     }
 
+    @Override
+    public JwtParser expectSubject(String subject) {
+        expect(Claims.SUBJECT, subject);
+
+        return this;
+    }
+
     @Override
     public JwtParser expect(String claimName, Object value) {
         if (claimName != null && claimName.length() > 0 && value != null) {

src/test/groovy/io/jsonwebtoken/JwtParserTest.groovy

@@ -1046,4 +1046,67 @@ class JwtParserTest {
         }
     }
 
+    @Test
+    void testParseExpectSubject_Success() {
+        def subject = 'A Most Awesome Subject'
+
+        byte[] key = randomKey()
+
+        String compact = Jwts.builder().signWith(SignatureAlgorithm.HS256, key).
+            setSubject(subject).
+            compact()
+
+        Jwt<Header,Claims> jwt = Jwts.parser().setSigningKey(key).
+            expectSubject(subject).
+            parseClaimsJws(compact)
+
+        assertEquals jwt.getBody().getSubject(), subject
+    }
+
+    @Test
+    void testParseExpectSubject_Incorrect_Fail() {
+        def goodSubject = 'A Most Awesome Subject'
+        def badSubject = 'A Most Bogus Subject'
+
+        byte[] key = randomKey()
+
+        String compact = Jwts.builder().signWith(SignatureAlgorithm.HS256, key).
+            setSubject(badSubject).
+            compact()
+
+        try {
+            Jwts.parser().setSigningKey(key).
+                expectSubject(goodSubject).
+                parseClaimsJws(compact)
+            fail()
+        } catch(IncorrectClaimException e) {
+            assertEquals(
+                String.format(INCORRECT_EXPECTED_CLAIM_MESSAGE_TEMPLATE, Claims.SUBJECT, goodSubject, badSubject),
+                e.getMessage()
+            )
+        }
+    }
+
+    @Test
+    void testParseExpectSubject_Missing_Fail() {
+        def subject = 'A Most Awesome Subject'
+
+        byte[] key = randomKey()
+
+        String compact = Jwts.builder().signWith(SignatureAlgorithm.HS256, key).
+            setId('id').
+            compact()
+
+        try {
+            Jwts.parser().setSigningKey(key).
+                expectSubject(subject).
+                parseClaimsJws(compact)
+            fail()
+        } catch(MissingClaimException e) {
+            assertEquals(
+                String.format(MISSING_EXPECTED_CLAIM_MESSAGE_TEMPLATE, Claims.SUBJECT, subject),
+                e.getMessage()
+            )
+        }
+    }
 }