Added addClaims function to JwtBuilder as described in Issue #196.

This function does not overwrite existing claims (as compared to setClaims).

src/main/java/io/jsonwebtoken/JwtBuilder.java

@@ -101,6 +101,18 @@ public interface JwtBuilder extends ClaimsMutator<JwtBuilder> {
      */
     JwtBuilder setClaims(Map<String, Object> claims);
 
+    /**
+     * Adds all given name/value pairs to the JSON Claims in the payload. If a Claims instance does not yet exist at the
+     * time this method is called, one will be created automatically before applying the name/value pairs.
+     *
+     * <p>The payload and claims properties are mutually exclusive - only one of the two may be used.</p>
+     *
+     * @param claims the JWT claims to be added to the JWT body.
+     * @return the builder for method chaining.
+     * @since 0.8
+     */
+    JwtBuilder addClaims(Map<String, Object> claims);
+
     /**
      * Sets the JWT Claims <a href="https://tools.ietf.org/html/draft-ietf-oauth-json-web-token-25#section-4.1.1">
      * <code>iss</code></a> (issuer) value.  A {@code null} value will remove the property from the Claims.

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

@@ -17,14 +17,7 @@ package io.jsonwebtoken.impl;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
-import io.jsonwebtoken.Claims;
-import io.jsonwebtoken.CompressionCodec;
-import io.jsonwebtoken.Header;
-import io.jsonwebtoken.JwsHeader;
-import io.jsonwebtoken.JwtBuilder;
-import io.jsonwebtoken.JwtParser;
-import io.jsonwebtoken.Jwts;
-import io.jsonwebtoken.SignatureAlgorithm;
+import io.jsonwebtoken.*;
 import io.jsonwebtoken.impl.crypto.DefaultJwtSigner;
 import io.jsonwebtoken.impl.crypto.JwtSigner;
 import io.jsonwebtoken.lang.Assert;
@@ -148,6 +141,12 @@ public class DefaultJwtBuilder implements JwtBuilder {
         return this;
     }
 
+    @Override
+    public JwtBuilder addClaims(Map<String, Object> claims) {
+        ensureClaims().putAll(claims);
+        return this;
+    }
+
     @Override
     public JwtBuilder setIssuer(String iss) {
         if (Strings.hasText(iss)) {

src/test/groovy/io/jsonwebtoken/impl/DefaultJwtBuilderTest.groovy

@@ -74,6 +74,26 @@ class DefaultJwtBuilderTest {
         assertSame b.claims, c
     }
 
+    @Test
+    void testAddClaims() {
+        def b = new DefaultJwtBuilder()
+        def c = Jwts.claims([initial: 'initial'])
+        b.setClaims(c)
+        def c2 = [foo: 'bar', baz: 'buz']
+        b.addClaims(c2)
+        assertEquals 'initial', b.claims.get('initial')
+        assertEquals 'bar', b.claims.get('foo')
+    }
+
+    @Test
+    void testAddClaimsWithoutInitializing() {
+        def b = new DefaultJwtBuilder()
+        def c = [foo: 'bar', baz: 'buz']
+        b.addClaims(c)
+        assertNotNull b.claims
+        assertEquals b.claims, c
+    }
+
     @Test
     void testClaim() {
         def b = new DefaultJwtBuilder()