diff --git a/src/main/java/net/onrc/onos/core/datagrid/web/GetNGFlowsSummaryResource.java b/src/main/java/net/onrc/onos/core/datagrid/web/GetNGFlowsSummaryResource.java
index fa7c6d1..291f82d 100644
--- a/src/main/java/net/onrc/onos/core/datagrid/web/GetNGFlowsSummaryResource.java
+++ b/src/main/java/net/onrc/onos/core/datagrid/web/GetNGFlowsSummaryResource.java
@@ -80,12 +80,14 @@
             flowPath.setFlowPathUserState(FlowPathUserState.FP_USER_ADD);
 
             // Setup the Source and Destination DPID and Port
-            SwitchPort srcPort = flowPath.dataPath().srcPort();
-            SwitchPort dstPort = flowPath.dataPath().dstPort();
-            srcPort.setDpid(new Dpid(spIntent.getSrcSwitchDpid()));
-            srcPort.setPort(new Port((short) spIntent.getSrcPortNumber()));
-            dstPort.setDpid(new Dpid(spIntent.getDstSwitchDpid()));
-            dstPort.setPort(new Port((short) spIntent.getDstPortNumber()));
+            Dpid srcDpid = new Dpid(spIntent.getSrcSwitchDpid());
+            Port srcPort = new Port((short) spIntent.getSrcPortNumber());
+            Dpid dstDpid = new Dpid(spIntent.getDstSwitchDpid());
+            Port dstPort = new Port((short) spIntent.getDstPortNumber());
+            SwitchPort srcSwitchPort = new SwitchPort(srcDpid, srcPort);
+            SwitchPort dstSwitchPort = new SwitchPort(dstDpid, dstPort);
+            flowPath.dataPath().setSrcPort(srcSwitchPort);
+            flowPath.dataPath().setDstPort(dstSwitchPort);
 
             // Extract the Flow Entries
             Path path = pathIntent.getPath();
diff --git a/src/main/java/net/onrc/onos/core/util/CallerId.java b/src/main/java/net/onrc/onos/core/util/CallerId.java
index f58d69f..6986f13 100644
--- a/src/main/java/net/onrc/onos/core/util/CallerId.java
+++ b/src/main/java/net/onrc/onos/core/util/CallerId.java
@@ -4,14 +4,16 @@
 
 /**
  * The class representing a Caller ID for an ONOS component.
+ * This class is immutable.
  */
-public class CallerId {
-    private String value;
+public final class CallerId {
+    private final String value;
 
     /**
      * Default constructor.
      */
     public CallerId() {
+        this.value = null;
     }
 
     /**
@@ -44,16 +46,6 @@
     }
 
     /**
-     * Set the value of the Caller ID.
-     *
-     * @param value the value to set.
-     */
-    @JsonProperty("value")
-    public void setValue(String value) {
-        this.value = value;
-    }
-
-    /**
      * Convert the Caller ID value to a string.
      *
      * @return the Caller ID value to a string.
diff --git a/src/main/java/net/onrc/onos/core/util/DataPathEndpoints.java b/src/main/java/net/onrc/onos/core/util/DataPathEndpoints.java
index 70edfee..4e0d40c 100644
--- a/src/main/java/net/onrc/onos/core/util/DataPathEndpoints.java
+++ b/src/main/java/net/onrc/onos/core/util/DataPathEndpoints.java
@@ -5,15 +5,18 @@
 
 /**
  * The class representing the Data Path Endpoints.
+ * This class is immutable.
  */
-public class DataPathEndpoints {
-    private SwitchPort srcPort;        // The source port
-    private SwitchPort dstPort;        // The destination port
+public final class DataPathEndpoints {
+    private final SwitchPort srcPort;        // The source port
+    private final SwitchPort dstPort;        // The destination port
 
     /**
      * Default constructor.
      */
     public DataPathEndpoints() {
+        srcPort = null;
+        dstPort = null;
     }
 
     /**
@@ -38,16 +41,6 @@
     }
 
     /**
-     * Set the data path source port.
-     *
-     * @param srcPort the data path source port to set.
-     */
-    @JsonProperty("srcPort")
-    public void setSrcPort(SwitchPort srcPort) {
-        this.srcPort = srcPort;
-    }
-
-    /**
      * Get the data path destination port.
      *
      * @return the data path destination port.
@@ -58,16 +51,6 @@
     }
 
     /**
-     * Set the data path destination port.
-     *
-     * @param dstPort the data path destination port to set.
-     */
-    @JsonProperty("dstPort")
-    public void setDstPort(SwitchPort dstPort) {
-        this.dstPort = dstPort;
-    }
-
-    /**
      * Convert the data path endpoints to a string.
      * <p/>
      * The string has the following form:
diff --git a/src/main/java/net/onrc/onos/core/util/Dpid.java b/src/main/java/net/onrc/onos/core/util/Dpid.java
index 80ebc15..f66a5d4 100644
--- a/src/main/java/net/onrc/onos/core/util/Dpid.java
+++ b/src/main/java/net/onrc/onos/core/util/Dpid.java
@@ -9,13 +9,13 @@
 
 /**
  * The class representing a network switch DPID.
+ * This class is immutable.
  */
 @JsonDeserialize(using = DpidDeserializer.class)
 @JsonSerialize(using = DpidSerializer.class)
-public class Dpid {
-    static public final long UNKNOWN = 0;
-
-    private long value;
+public final class Dpid {
+    private final static long UNKNOWN = 0;
+    private final long value;
 
     /**
      * Default constructor.
@@ -52,15 +52,6 @@
     }
 
     /**
-     * Set the value of the DPID.
-     *
-     * @param value the value to set.
-     */
-    public void setValue(long value) {
-        this.value = value;
-    }
-
-    /**
      * Convert the DPID value to a ':' separated hexadecimal string.
      *
      * @return the DPID value as a ':' separated hexadecimal string.
diff --git a/src/main/java/net/onrc/onos/core/util/FlowEntryId.java b/src/main/java/net/onrc/onos/core/util/FlowEntryId.java
index 373962e..62c009a 100644
--- a/src/main/java/net/onrc/onos/core/util/FlowEntryId.java
+++ b/src/main/java/net/onrc/onos/core/util/FlowEntryId.java
@@ -11,17 +11,19 @@
 
 /**
  * The class representing a Flow Entry ID.
+ * This class is immutable.
  */
 @JsonDeserialize(using = FlowEntryIdDeserializer.class)
 @JsonSerialize(using = FlowEntryIdSerializer.class)
-public class FlowEntryId {
-    private long value;
+public final class FlowEntryId {
+    private final static long INVALID = -1;
+    private final long value;
 
     /**
      * Default constructor.
      */
     public FlowEntryId() {
-        this.value = -1;
+        this.value = FlowEntryId.INVALID;
     }
 
     /**
@@ -62,22 +64,13 @@
     }
 
     /**
-     * Set the value of the Flow Entry ID.
-     *
-     * @param value the value to set.
-     */
-    public void setValue(long value) {
-        this.value = value;
-    }
-
-    /**
      * Test whether the Flow Entry ID is valid.
      *
      * @return true if the Flow Entry ID is valid, otherwise false.
      */
     @JsonIgnore
     public boolean isValid() {
-        return (this.value() != -1);
+        return (this.value() != FlowEntryId.INVALID);
     }
 
     /**
diff --git a/src/main/java/net/onrc/onos/core/util/FlowId.java b/src/main/java/net/onrc/onos/core/util/FlowId.java
index c5ee39d..5eace27 100644
--- a/src/main/java/net/onrc/onos/core/util/FlowId.java
+++ b/src/main/java/net/onrc/onos/core/util/FlowId.java
@@ -11,17 +11,19 @@
 
 /**
  * The class representing a Flow ID.
+ * This class is immutable.
  */
 @JsonDeserialize(using = FlowIdDeserializer.class)
 @JsonSerialize(using = FlowIdSerializer.class)
-public class FlowId implements Comparable<FlowId> {
-    private long value;
+public final class FlowId implements Comparable<FlowId> {
+    private final static long INVALID = -1;
+    private final long value;
 
     /**
      * Default constructor.
      */
     public FlowId() {
-        this.value = -1;
+        this.value = FlowId.INVALID;
     }
 
     /**
@@ -62,22 +64,13 @@
     }
 
     /**
-     * Set the value of the Flow ID.
-     *
-     * @param value the value to set.
-     */
-    public void setValue(long value) {
-        this.value = value;
-    }
-
-    /**
      * Test whether the Flow ID is valid.
      *
      * @return true if the Flow ID is valid, otherwise false.
      */
     @JsonIgnore
     public boolean isValid() {
-        return (this.value() != -1);
+        return (this.value() != FlowId.INVALID);
     }
 
     /**
diff --git a/src/main/java/net/onrc/onos/core/util/IPv4.java b/src/main/java/net/onrc/onos/core/util/IPv4.java
index a7f3d24..b25099a 100644
--- a/src/main/java/net/onrc/onos/core/util/IPv4.java
+++ b/src/main/java/net/onrc/onos/core/util/IPv4.java
@@ -8,11 +8,12 @@
 
 /**
  * The class representing an IPv4 address.
+ * This class is immutable.
  */
 @JsonDeserialize(using = IPv4Deserializer.class)
 @JsonSerialize(using = IPv4Serializer.class)
-public class IPv4 {
-    private int value;
+public final class IPv4 {
+    private final int value;
 
     /**
      * Default constructor.
@@ -67,15 +68,6 @@
     }
 
     /**
-     * Set the value of the IPv4 address.
-     *
-     * @param value the value to set.
-     */
-    public void setValue(int value) {
-        this.value = value;
-    }
-
-    /**
      * Convert the IPv4 value to a '.' separated string.
      *
      * @return the IPv4 value as a '.' separated string.
diff --git a/src/main/java/net/onrc/onos/core/util/IPv4Net.java b/src/main/java/net/onrc/onos/core/util/IPv4Net.java
index 3aa5a8b..6a04635 100644
--- a/src/main/java/net/onrc/onos/core/util/IPv4Net.java
+++ b/src/main/java/net/onrc/onos/core/util/IPv4Net.java
@@ -8,17 +8,19 @@
 
 /**
  * The class representing an IPv4 network address.
+ * This class is immutable.
  */
 @JsonDeserialize(using = IPv4NetDeserializer.class)
 @JsonSerialize(using = IPv4NetSerializer.class)
-public class IPv4Net {
-    private IPv4 address;        // The IPv4 address
-    private short prefixLen;        // The prefix length
+public final class IPv4Net {
+    private final IPv4 address;         // The IPv4 address
+    private final short prefixLen;      // The prefix length
 
     /**
      * Default constructor.
      */
     public IPv4Net() {
+        this.address = null;
         this.prefixLen = 0;
     }
 
@@ -30,6 +32,8 @@
     public IPv4Net(IPv4Net other) {
         if (other.address != null)
             this.address = new IPv4(other.address);
+        else
+            this.address = null;
         this.prefixLen = other.prefixLen;
     }
 
@@ -69,15 +73,6 @@
     }
 
     /**
-     * Set the address value of the IPv4Net address.
-     *
-     * @param address the address to use.
-     */
-    public void setAddress(IPv4 address) {
-        this.address = address;
-    }
-
-    /**
      * Get the prefix length value of the IPv4Net address.
      *
      * @return the prefix length value of the IPv4Net address.
@@ -87,26 +82,6 @@
     }
 
     /**
-     * Set the prefix length value of the IPv4Net address.
-     *
-     * @param prefixLen the prefix length to use.
-     */
-    public void setPrefixLen(short prefixLen) {
-        this.prefixLen = prefixLen;
-    }
-
-    /**
-     * Set the value of the IPv4Net address.
-     *
-     * @param address   the address to use.
-     * @param prefixLen the prefix length to use.
-     */
-    public void setValue(IPv4 address, short prefixLen) {
-        this.address = address;
-        this.prefixLen = prefixLen;
-    }
-
-    /**
      * Convert the IPv4Net value to an "address/prefixLen" string.
      *
      * @return the IPv4Net value as an "address/prefixLen" string.
diff --git a/src/main/java/net/onrc/onos/core/util/IPv6.java b/src/main/java/net/onrc/onos/core/util/IPv6.java
index 38a86b5..986fd11 100644
--- a/src/main/java/net/onrc/onos/core/util/IPv6.java
+++ b/src/main/java/net/onrc/onos/core/util/IPv6.java
@@ -9,12 +9,13 @@
 
 /**
  * The class representing an IPv6 address.
+ * This class is immutable.
  */
 @JsonDeserialize(using = IPv6Deserializer.class)
 @JsonSerialize(using = IPv6Serializer.class)
-public class IPv6 {
-    private long valueHigh;    // The higher (more significant) 64 bits
-    private long valueLow;    // The lower (less significant) 64 bits
+public final class IPv6 {
+    private final long valueHigh;    // The higher (more significant) 64 bits
+    private final long valueLow;     // The lower (less significant) 64 bits
 
     /**
      * Default constructor.
@@ -67,15 +68,6 @@
     }
 
     /**
-     * Set the value of the higher (more significant) 64 bits of the address.
-     *
-     * @param valueHigh the higher (more significant) 64 bits of the address.
-     */
-    public void setValueHigh(long valueHigh) {
-        this.valueHigh = valueHigh;
-    }
-
-    /**
      * Get the value of the lower (less significant) 64 bits of the address.
      *
      * @return the value of the lower (less significant) 64 bits of the
@@ -86,26 +78,6 @@
     }
 
     /**
-     * Get the value of the lower (less significant) 64 bits of the address.
-     *
-     * @param valueLow the lower (less significant) 64 bits of the address.
-     */
-    public void setValueLow(long valueLow) {
-        this.valueLow = valueLow;
-    }
-
-    /**
-     * Set the value of the IPv6 address.
-     *
-     * @param valueHigh the higher (more significant) 64 bits of the address.
-     * @param valueLow  the lower (less significant) 64 bits of the address.
-     */
-    public void setValue(long valueHigh, long valueLow) {
-        this.valueHigh = valueHigh;
-        this.valueLow = valueLow;
-    }
-
-    /**
      * Convert the IPv6 value to a ':' separated string.
      *
      * @return the IPv6 value as a ':' separated string.
diff --git a/src/main/java/net/onrc/onos/core/util/IPv6Net.java b/src/main/java/net/onrc/onos/core/util/IPv6Net.java
index 1faa7c5..72ec5e9 100644
--- a/src/main/java/net/onrc/onos/core/util/IPv6Net.java
+++ b/src/main/java/net/onrc/onos/core/util/IPv6Net.java
@@ -8,17 +8,19 @@
 
 /**
  * The class representing an IPv6 network address.
+ * This class is immutable.
  */
 @JsonDeserialize(using = IPv6NetDeserializer.class)
 @JsonSerialize(using = IPv6NetSerializer.class)
-public class IPv6Net {
-    private IPv6 address;        // The IPv6 address
-    private short prefixLen;        // The prefix length
+public final class IPv6Net {
+    private final IPv6 address;         // The IPv6 address
+    private final short prefixLen;      // The prefix length
 
     /**
      * Default constructor.
      */
     public IPv6Net() {
+        this.address = null;
         this.prefixLen = 0;
     }
 
@@ -30,6 +32,8 @@
     public IPv6Net(IPv6Net other) {
         if (other.address != null)
             this.address = new IPv6(other.address);
+        else
+            this.address = null;
         this.prefixLen = other.prefixLen;
     }
 
@@ -69,15 +73,6 @@
     }
 
     /**
-     * Set the address value of the IPv6Net address.
-     *
-     * @param address the address to use.
-     */
-    public void setAddress(IPv6 address) {
-        this.address = address;
-    }
-
-    /**
      * Get the prefix length value of the IPv6Net address.
      *
      * @return the prefix length value of the IPv6Net address.
@@ -87,26 +82,6 @@
     }
 
     /**
-     * Set the prefix length value of the IPv6Net address.
-     *
-     * @param prefixLen the prefix length to use.
-     */
-    public void setPrefixLen(short prefixLen) {
-        this.prefixLen = prefixLen;
-    }
-
-    /**
-     * Set the value of the IPv6Net address.
-     *
-     * @param address   the address to use.
-     * @param prefixLen the prefix length to use.
-     */
-    public void setValue(IPv6 address, short prefixLen) {
-        this.address = address;
-        this.prefixLen = prefixLen;
-    }
-
-    /**
      * Convert the IPv6Net value to an "address/prefixLen" string.
      *
      * @return the IPv6Net value as an "address/prefixLen" string.
diff --git a/src/main/java/net/onrc/onos/core/util/Port.java b/src/main/java/net/onrc/onos/core/util/Port.java
index 77d983b..20a2a21 100644
--- a/src/main/java/net/onrc/onos/core/util/Port.java
+++ b/src/main/java/net/onrc/onos/core/util/Port.java
@@ -4,9 +4,9 @@
 
 /**
  * The class representing a network port of a switch.
+ * This class is immutable.
  */
-
-public class Port {
+public final class Port {
     /**
      * Special port values.
      * <p/>
@@ -70,7 +70,7 @@
         }
     }
 
-    private short value;
+    private final short value;
 
     /**
      * Default constructor.
@@ -117,16 +117,6 @@
     }
 
     /**
-     * Set the value of the port.
-     *
-     * @param value the value to set.
-     */
-    @JsonProperty("value")
-    public void setValue(short value) {
-        this.value = value;
-    }
-
-    /**
      * Convert the port value to a string.
      *
      * @return the port value as a string.
@@ -136,7 +126,6 @@
         return Short.toString(this.value);
     }
 
-
     @Override
     public boolean equals(Object other) {
         if (!(other instanceof Port)) {
diff --git a/src/main/java/net/onrc/onos/core/util/Switch.java b/src/main/java/net/onrc/onos/core/util/Switch.java
index d1a463c..8ea1184 100644
--- a/src/main/java/net/onrc/onos/core/util/Switch.java
+++ b/src/main/java/net/onrc/onos/core/util/Switch.java
@@ -4,9 +4,10 @@
 
 /**
  * The class representing a Switch.
+ * This class is almost immutable: the switch state is mutable.
  * NOTE: Currently this class is (almost) not used.
  */
-public class Switch {
+public final class Switch {
     /**
      * The Switch state.
      */
@@ -15,8 +16,8 @@
         ACTIVE,
     }
 
-    private Dpid dpid;            // The DPID of the switch
-    private SwitchState state;        // The state of the switch
+    private final Dpid dpid;            // The DPID of the switch
+    private SwitchState state;          // The state of the switch
 
     /**
      * Default constructor.
@@ -62,16 +63,6 @@
     }
 
     /**
-     * Set the DPID.
-     *
-     * @param dpid the DPID to use.
-     */
-    @JsonProperty("dpid")
-    public void setDpid(Dpid dpid) {
-        this.dpid = dpid;
-    }
-
-    /**
      * Get the state.
      *
      * @return the state.
diff --git a/src/main/java/net/onrc/onos/core/util/SwitchPort.java b/src/main/java/net/onrc/onos/core/util/SwitchPort.java
index eb72b72..9178267 100644
--- a/src/main/java/net/onrc/onos/core/util/SwitchPort.java
+++ b/src/main/java/net/onrc/onos/core/util/SwitchPort.java
@@ -4,15 +4,18 @@
 
 /**
  * The class representing a Switch-Port.
+ * This class is immutable.
  */
-public class SwitchPort {
-    private Dpid dpid;        // The DPID of the switch
-    private Port port;        // The port of the switch
+public final class SwitchPort {
+    private final Dpid dpid;        // The DPID of the switch
+    private final Port port;        // The port of the switch
 
     /**
      * Default constructor.
      */
     public SwitchPort() {
+        this.dpid = null;
+        this.port = null;
     }
 
     /**
@@ -37,16 +40,6 @@
     }
 
     /**
-     * Set the DPID value of the Switch-Port.
-     *
-     * @param dpid the DPID to use.
-     */
-    @JsonProperty("dpid")
-    public void setDpid(Dpid dpid) {
-        this.dpid = dpid;
-    }
-
-    /**
      * Get the port value of the Switch-Port.
      *
      * @return the port value of the Switch-Port.
@@ -57,27 +50,6 @@
     }
 
     /**
-     * Set the port value of the Switch-Port.
-     *
-     * @param port the port to use.
-     */
-    @JsonProperty("port")
-    public void setPort(Port port) {
-        this.port = port;
-    }
-
-    /**
-     * Set the DPID and port values of the Switch-Port.
-     *
-     * @param dpid the DPID to use.
-     * @param port the port to use.
-     */
-    public void setValue(Dpid dpid, Port port) {
-        this.dpid = dpid;
-        this.port = port;
-    }
-
-    /**
      * Convert the Switch-Port value to a string.
      * <p/>
      * The string has the following form:
@@ -90,7 +62,6 @@
         return this.dpid.toString() + "/" + this.port;
     }
 
-
     @Override
     public boolean equals(Object other) {
         if (!(other instanceof SwitchPort)) {