add DefaultPropertiesCombiner and DefaultVertexValueCombiner (#16)

* add OverwriteValueCombiner, MergeNewPropertiesCombiner and MergeOldPropertiesCombiner

computer-core/src/main/java/com/baidu/hugegraph/computer/core/combiner/DoubleValueSumCombiner.java

@@ -20,11 +20,14 @@
 package com.baidu.hugegraph.computer.core.combiner;
 
 import com.baidu.hugegraph.computer.core.graph.value.DoubleValue;
+import com.baidu.hugegraph.util.E;
 
 public class DoubleValueSumCombiner implements Combiner<DoubleValue> {
 
     @Override
     public DoubleValue combine(DoubleValue v1, DoubleValue v2) {
+        E.checkArgumentNotNull(v1, "The combine parameter v1 can't be null");
+        E.checkArgumentNotNull(v2, "The combine parameter v2 can't be null");
         v2.value(v1.value() + v2.value());
         return v2;
     }

computer-core/src/main/java/com/baidu/hugegraph/computer/core/combiner/LongValueSumCombiner.java

@@ -20,11 +20,14 @@
 package com.baidu.hugegraph.computer.core.combiner;
 
 import com.baidu.hugegraph.computer.core.graph.value.LongValue;
+import com.baidu.hugegraph.util.E;
 
 public class LongValueSumCombiner implements Combiner<LongValue> {
 
     @Override
     public LongValue combine(LongValue v1, LongValue v2) {
+        E.checkArgumentNotNull(v1, "The combine parameter v1 can't be null");
+        E.checkArgumentNotNull(v2, "The combine parameter v2 can't be null");
         v2.value(v1.value() + v2.value());
         return v2;
     }

computer-core/src/main/java/com/baidu/hugegraph/computer/core/combiner/MergeNewPropertiesCombiner.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package com.baidu.hugegraph.computer.core.combiner;
+
+import java.util.Map;
+
+import com.baidu.hugegraph.computer.core.graph.properties.Properties;
+import com.baidu.hugegraph.computer.core.graph.value.Value;
+import com.baidu.hugegraph.util.E;
+
+public class MergeNewPropertiesCombiner implements PropertiesCombiner {
+
+    /**
+     * Merge properties v2 into v1. If a property exists in both v1 and v2,
+     * remain the value in v1.
+     */
+    @Override
+    public Properties combine(Properties v1, Properties v2) {
+        E.checkArgumentNotNull(v1, "The combine parameter v1 can't be null");
+        E.checkArgumentNotNull(v2, "The combine parameter v2 can't be null");
+        Map<String, Value> v1Map = v1.get();
+        Map<String, Value> v2Map = v2.get();
+        for (Map.Entry<String, Value> entry : v2Map.entrySet()) {
+             v1Map.putIfAbsent(entry.getKey(), entry.getValue());
+        }
+        return v1;
+    }
+}

computer-core/src/main/java/com/baidu/hugegraph/computer/core/combiner/MergeOldPropertiesCombiner.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package com.baidu.hugegraph.computer.core.combiner;
+
+import java.util.Map;
+
+import com.baidu.hugegraph.computer.core.graph.properties.Properties;
+import com.baidu.hugegraph.computer.core.graph.value.Value;
+import com.baidu.hugegraph.util.E;
+
+public class MergeOldPropertiesCombiner implements PropertiesCombiner {
+
+    /**
+     * Merge properties v1 into v2. If a property exists in both v1 and v2,
+     * remain the value in v2.
+     */
+    @Override
+    public Properties combine(Properties v1, Properties v2) {
+        E.checkArgumentNotNull(v1, "The combine parameter v1 can't be null");
+        E.checkArgumentNotNull(v2, "The combine parameter v2 can't be null");
+        Map<String, Value> v1Map = v1.get();
+        Map<String, Value> v2Map = v2.get();
+        for (Map.Entry<String, Value> entry : v1Map.entrySet()) {
+            v2Map.putIfAbsent(entry.getKey(), entry.getValue());
+        }
+        return v2;
+    }
+}

computer-core/src/main/java/com/baidu/hugegraph/computer/core/combiner/OverwriteCombiner.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package com.baidu.hugegraph.computer.core.combiner;
+
+import com.baidu.hugegraph.util.E;
+
+public class OverwriteCombiner<T> implements Combiner<T> {
+
+    @Override
+    public T combine(T v1, T v2) {
+        E.checkArgumentNotNull(v1, "The combine parameter v1 can't be null");
+        E.checkArgumentNotNull(v2, "The combine parameter v2 can't be null");
+        return v2;
+    }
+}

computer-core/src/main/java/com/baidu/hugegraph/computer/core/combiner/PropertiesCombiner.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package com.baidu.hugegraph.computer.core.combiner;
+
+import com.baidu.hugegraph.computer.core.graph.properties.Properties;
+
+/**
+ * When vertex properties with the same vertex id are loaded, this class
+ * specifies how to combine their properties.
+ */
+public interface PropertiesCombiner extends Combiner<Properties> {
+}

computer-core/src/main/java/com/baidu/hugegraph/computer/core/combiner/ValueMaxCombiner.java

@@ -20,11 +20,14 @@
 package com.baidu.hugegraph.computer.core.combiner;
 
 import com.baidu.hugegraph.computer.core.graph.value.Value;
+import com.baidu.hugegraph.util.E;
 
 public class ValueMaxCombiner <T extends Value> implements Combiner<T> {
 
     @Override
     public T combine(T v1, T v2) {
+        E.checkArgumentNotNull(v1, "The combine parameter v1 can't be null");
+        E.checkArgumentNotNull(v2, "The combine parameter v2 can't be null");
         if (v1.compareTo(v2) >= 0) {
             return v1;
         } else {

computer-core/src/main/java/com/baidu/hugegraph/computer/core/combiner/ValueMinCombiner.java

@@ -20,11 +20,14 @@
 package com.baidu.hugegraph.computer.core.combiner;
 
 import com.baidu.hugegraph.computer.core.graph.value.Value;
+import com.baidu.hugegraph.util.E;
 
 public class ValueMinCombiner<T extends Value> implements Combiner<T> {
 
     @Override
     public T combine(T v1, T v2) {
+        E.checkArgumentNotNull(v1, "The combine parameter v1 can't be null");
+        E.checkArgumentNotNull(v2, "The combine parameter v2 can't be null");
         if (v1.compareTo(v2) <= 0) {
             return v1;
         } else {

computer-test/src/main/java/com/baidu/hugegraph/computer/core/combiner/CombinerTestSuite.java

@@ -24,6 +24,9 @@
 
 @RunWith(Suite.class)
 @Suite.SuiteClasses({
+    OverwriteCombinerTest.class,
+    MergeOldPropertiesCombinerTest.class,
+    MergeNewPropertiesCombinerTest.class,
     DoubleValueSumCombinerTest.class,
     LongValueSumCombinerTest.class,
     ValueMinCombinerTest.class,

computer-test/src/main/java/com/baidu/hugegraph/computer/core/combiner/DoubleValueSumCombinerTest.java

@@ -27,7 +27,7 @@
 public class DoubleValueSumCombinerTest {
 
     @Test
-    public void test() {
+    public void testCombine() {
         DoubleValue sum = new DoubleValue(0.0D);
         DoubleValueSumCombiner combiner = new DoubleValueSumCombiner();
         for (int i = 1; i <= 10; i++) {
@@ -36,4 +36,24 @@ public void test() {
         }
         Assert.assertEquals(55.0D, sum.value(), 0.0D);
     }
+
+    @Test
+    public void testCombineNull() {
+        DoubleValue value1 = new DoubleValue(0.0D);
+        DoubleValue value2 = new DoubleValue(0.0D);
+        DoubleValueSumCombiner combiner = new DoubleValueSumCombiner();
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            combiner.combine(null, value2);
+        }, e -> {
+            Assert.assertEquals("The combine parameter v1 can't be null",
+                                e.getMessage());
+        });
+
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            combiner.combine(value1, null);
+        }, e -> {
+            Assert.assertEquals("The combine parameter v2 can't be null",
+                                e.getMessage());
+        });
+    }
 }

computer-test/src/main/java/com/baidu/hugegraph/computer/core/combiner/LongValueSumCombinerTest.java

@@ -27,7 +27,7 @@
 public class LongValueSumCombinerTest {
 
     @Test
-    public void test() {
+    public void testCombine() {
         LongValue sum = new LongValue(0L);
         LongValueSumCombiner combiner = new LongValueSumCombiner();
         for (int i = 1; i <= 10; i++) {
@@ -36,4 +36,24 @@ public void test() {
         }
         Assert.assertEquals(55L, sum.value());
     }
+
+    @Test
+    public void testCombineNull() {
+        LongValue value1 = new LongValue(1L);
+        LongValue value2 = new LongValue(2L);
+        LongValueSumCombiner combiner = new LongValueSumCombiner();
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            combiner.combine(null, value2);
+        }, e -> {
+            Assert.assertEquals("The combine parameter v1 can't be null",
+                                e.getMessage());
+        });
+
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            combiner.combine(value1, null);
+        }, e -> {
+            Assert.assertEquals("The combine parameter v2 can't be null",
+                                e.getMessage());
+        });
+    }
 }

computer-test/src/main/java/com/baidu/hugegraph/computer/core/combiner/MergeNewPropertiesCombinerTest.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2017 HugeGraph Authors
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to You under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package com.baidu.hugegraph.computer.core.combiner;
+
+import org.junit.Test;
+
+import com.baidu.hugegraph.computer.core.graph.id.Utf8Id;
+import com.baidu.hugegraph.computer.core.graph.properties.DefaultProperties;
+import com.baidu.hugegraph.computer.core.graph.properties.Properties;
+import com.baidu.hugegraph.testutil.Assert;
+
+public class MergeNewPropertiesCombinerTest {
+
+    @Test
+    public void testCombine() {
+        Properties properties1 = new DefaultProperties();
+        properties1.put("name", new Utf8Id("marko").idValue());
+        properties1.put("city", new Utf8Id("Beijing").idValue());
+
+        Properties properties2 = new DefaultProperties();
+        properties2.put("name", new Utf8Id("josh").idValue());
+        properties2.put("age", new Utf8Id("18").idValue());
+
+        Properties expect = new DefaultProperties();
+        expect.put("name", new Utf8Id("marko").idValue());
+        expect.put("age", new Utf8Id("18").idValue());
+        expect.put("city", new Utf8Id("Beijing").idValue());
+
+        PropertiesCombiner combiner = new MergeNewPropertiesCombiner();
+        Properties properties = combiner.combine(properties1, properties2);
+        Assert.assertEquals(expect, properties);
+    }
+
+    @Test
+    public void testCombineNull() {
+        Properties properties1 = new DefaultProperties();
+        properties1.put("name", new Utf8Id("marko").idValue());
+        properties1.put("city", new Utf8Id("Beijing").idValue());
+
+        Properties properties2 = new DefaultProperties();
+        properties2.put("name", new Utf8Id("josh").idValue());
+        properties2.put("age", new Utf8Id("18").idValue());
+
+
+        PropertiesCombiner combiner = new MergeNewPropertiesCombiner();
+
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            combiner.combine(null, properties2);
+        }, e -> {
+            Assert.assertEquals("The combine parameter v1 can't be null",
+                                e.getMessage());
+        });
+
+        Assert.assertThrows(IllegalArgumentException.class, () -> {
+            combiner.combine(properties1, null);
+        }, e -> {
+            Assert.assertEquals("The combine parameter v2 can't be null",
+                                e.getMessage());
+        });
+    }
+}