diff --git a/compiler/src/main/cpp/capnpc-java.c++ b/compiler/src/main/cpp/capnpc-java.c++
index abc7724..2c93b73 100644
--- a/compiler/src/main/cpp/capnpc-java.c++
+++ b/compiler/src/main/cpp/capnpc-java.c++
@@ -1420,12 +1420,12 @@ private:
       }
 
       case schema::Value::DATA: {
-        kj::String constType = kj::strTree(
-            "::capnp::_::ConstData<", schema.as<Data>().size(), ">").flatten();
         return ConstText {
           true,
-          kj::strTree("const ", constType, ' ', scope, upperCase, "(::capnp::schemas::b_",
-                      kj::hex(proto.getId()), ".words + ", schema.getValueSchemaOffset(), ");\n")
+          kj::strTree("public static final org.capnproto.Data.Reader ", upperCase,
+                      " = new org.capnproto.Data.Reader(Schemas.b_",
+                      kj::hex(proto.getId()), ", ", schema.getValueSchemaOffset(),
+                      ", ", constProto.getValue().getData().size(), ");\n")
         };
       }
 
diff --git a/compiler/src/test/scala/org/capnproto/EncodingTest.scala b/compiler/src/test/scala/org/capnproto/EncodingTest.scala
index 9b80ae1..0687d4d 100644
--- a/compiler/src/test/scala/org/capnproto/EncodingTest.scala
+++ b/compiler/src/test/scala/org/capnproto/EncodingTest.scala
@@ -85,6 +85,7 @@ class EncodingSuite extends FunSuite {
     (-123e45) should equal (TestConstants.FLOAT64_CONST);
 
     (TestConstants.TEXT_CONST.toString()) should equal ("foo");
+    (TestConstants.DATA_CONST.asArray()) should equal (TestUtil.data("bar"));
 
     (TestConstants.ENUM_CONST) should equal (TestEnum.CORGE);
 
diff --git a/compiler/src/test/scala/org/capnproto/TestUtil.scala b/compiler/src/test/scala/org/capnproto/TestUtil.scala
index 6e465b5..8d9be76 100644
--- a/compiler/src/test/scala/org/capnproto/TestUtil.scala
+++ b/compiler/src/test/scala/org/capnproto/TestUtil.scala
@@ -2,9 +2,16 @@ package org.capnproto;
 
 import org.capnproto.test.Test._;
 
-
-
 object TestUtil {
+
+  def data(str : String) : Array[Byte] = {
+    try {
+      return str.getBytes("ISO_8859-1");
+    } catch {
+      case e: Exception => throw new Error("could not decode");
+    }
+  }
+
   def initTestMessage(builder : TestAllTypes.Builder) {
     builder.setVoidField(org.capnproto.Void.VOID);
     builder.setBoolField(true);
@@ -18,7 +25,7 @@ object TestUtil {
     builder.setUInt64Field(0x1234567890123456L);
     builder.setFloat32Field(1234.5f);
     builder.setFloat64Field(-123e45);
-    builder.setTextField(new Text.Reader("foo"));
+    builder.setTextField("foo");
 //    builder.setDataField(data("bar"));
     {
 
diff --git a/compiler/src/test/schema/test.capnp b/compiler/src/test/schema/test.capnp
index 6e865f5..72c6ec0 100644
--- a/compiler/src/test/schema/test.capnp
+++ b/compiler/src/test/schema/test.capnp
@@ -204,6 +204,7 @@ struct TestConstants {
   const float32Const   :Float32 = 1234.5;
   const float64Const   :Float64 = -123e45;
   const textConst      :Text    = "foo";
+  const dataConst      :Data    = "bar";
 # ...
   const enumConst      :TestEnum = corge;
 }
diff --git a/runtime/src/main/java/org/capnproto/Data.java b/runtime/src/main/java/org/capnproto/Data.java
index 91ad805..4bccfc8 100644
--- a/runtime/src/main/java/org/capnproto/Data.java
+++ b/runtime/src/main/java/org/capnproto/Data.java
@@ -5,9 +5,46 @@ import java.nio.ByteBuffer;
 public final class Data {
 
     public static final class Reader {
+        public final ByteBuffer buffer;
+        public final int offset; // in bytes
+        public final int size; // in bytes
+
+        public Reader(ByteBuffer buffer, int offset, int size) {
+            this.buffer = buffer;
+            this.offset = offset * 8;
+            this.size = size;
+        }
+
+        public final int size() {
+            return this.size;
+        }
+
+        public ByteBuffer asByteBuffer() {
+            // not thread safe
+            this.buffer.position(this.offset);
+            ByteBuffer result = this.buffer.slice();
+            result.limit(this.size);
+            return result;
+        }
+
+        public byte[] asArray() {
+            // not thread safe
+            byte result[] = new byte[this.size];
+            this.buffer.position(this.offset);
+            this.buffer.get(result, 0, this.size);
+            return result;
+        }
     }
 
     public static final class Builder {
-    }
+        public final ByteBuffer buffer;
+        public final int offset; // in bytes
+        public final int size; // in bytes
 
+        public Builder(ByteBuffer buffer, int offset, int size) {
+            this.buffer = buffer;
+            this.offset = offset;
+            this.size = size;
+        }
+    }
 }
diff --git a/runtime/src/main/java/org/capnproto/Text.java b/runtime/src/main/java/org/capnproto/Text.java
index e742682..d844754 100644
--- a/runtime/src/main/java/org/capnproto/Text.java
+++ b/runtime/src/main/java/org/capnproto/Text.java
@@ -40,7 +40,7 @@ public final class Text {
             try {
                 return new String(bytes, "UTF-8");
             } catch (java.io.UnsupportedEncodingException e) {
-                return "unsupported encoding"; // XXX
+                throw new Error("UTF-8 is unsupported");
             }
         }
 
@@ -48,10 +48,8 @@ public final class Text {
 
     public static final class Builder {
         public final ByteBuffer buffer;
-        public final int offset;
-
-        // size not including the NUL terminator
-        public final int size;
+        public final int offset; // in bytes
+        public final int size; // in bytes
 
         public Builder(ByteBuffer buffer, int offset, int size) {
             this.buffer = buffer;
@@ -69,7 +67,7 @@ public final class Text {
             try {
                 return new String(bytes, "UTF-8");
             } catch (java.io.UnsupportedEncodingException e) {
-                return "unsupported encoding"; // XXX
+                throw new Error("UTF-8 is unsupported");
             }
         }