[Improve] Add new sharding strategy, use odevity of job name's hash code

to decide ip address asc or desc #10

elastic-job-core/src/main/java/com/dangdang/ddframe/job/internal/sharding/strategy/OdevitySortByNameJobShardingStrategy.java

@@ -0,0 +1,50 @@
+/**
+ * Copyright 1999-2015 dangdang.com.
+ * <p>
+ * Licensed 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.
+ * </p>
+ */
+
+package com.dangdang.ddframe.job.internal.sharding.strategy;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * 根据作业名的哈希值奇偶数决定IP升降序算法的分片策略.
+ * 
+ * <p>
+ * 作业名的哈希值为奇数则IP升序.
+ * 作业名的哈希值为偶数则IP降序.
+ * 用于不同的作业平均分配负载至不同的服务器.
+ * 如: 
+ * 1. 如果有3台服务器, 分成2片, 作业名称的哈希值为奇数, 则每台服务器分到的分片是: 1=[0], 2=[1], 3=[].
+ * 2. 如果有3台服务器, 分成2片, 作业名称的哈希值为偶数, 则每台服务器分到的分片是: 3=[0], 2=[1], 1=[].
+ * </p>
+ * 
+ * @author zhangliang
+ */
+public final class OdevitySortByNameJobShardingStrategy implements JobShardingStrategy {
+
+    private AverageAllocationJobShardingStrategy averageAllocationJobShardingStrategy = new AverageAllocationJobShardingStrategy();
+
+    @Override
+    public Map<String, List<Integer>> sharding(final List<String> serversList, final JobShardingStrategyOption option) {
+        long jobNameHash = option.getJobName().hashCode();
+        if (0 == jobNameHash % 2) {
+            Collections.reverse(serversList);
+        }
+        return averageAllocationJobShardingStrategy.sharding(serversList, option);
+    }
+}

elastic-job-core/src/test/java/com/dangdang/ddframe/job/AllJobTests.java

@@ -52,6 +52,7 @@
 import com.dangdang.ddframe.job.internal.sharding.ShardingServiceTest;
 import com.dangdang.ddframe.job.internal.sharding.strategy.AverageAllocationJobShardingStrategyTest;
 import com.dangdang.ddframe.job.internal.sharding.strategy.JobShardingStrategyFactoryTest;
+import com.dangdang.ddframe.job.internal.sharding.strategy.OdevitySortByNameJobShardingStrategyTest;
 import com.dangdang.ddframe.job.internal.statistics.ProcessCountJobTest;
 import com.dangdang.ddframe.job.internal.statistics.ProcessCountStatisticsTest;
 import com.dangdang.ddframe.job.internal.storage.JobNodePathTest;
@@ -83,6 +84,7 @@
     OffsetNodeTest.class, 
     JobShardingStrategyFactoryTest.class, 
     AverageAllocationJobShardingStrategyTest.class, 
+    OdevitySortByNameJobShardingStrategyTest.class, 
     ProcessCountJobTest.class, 
     ProcessCountStatisticsTest.class, 
     DisabledJobTest.class, 

elastic-job-core/src/test/java/com/dangdang/ddframe/job/internal/sharding/strategy/OdevitySortByNameJobShardingStrategyTest.java

@@ -0,0 +1,37 @@
+package com.dangdang.ddframe.job.internal.sharding.strategy;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.Test;
+
+public final class OdevitySortByNameJobShardingStrategyTest {
+
+    private OdevitySortByNameJobShardingStrategy odevitySortByNameJobShardingStrategy = new OdevitySortByNameJobShardingStrategy();
+
+    @Test
+    public void assertshardingByAsc() {
+        Map<String, List<Integer>> expected = new LinkedHashMap<>(3);
+        expected.put("host0", Arrays.asList(0));
+        expected.put("host1", Arrays.asList(1));
+        expected.put("host2", Collections.<Integer>emptyList());
+        assertThat(
+                odevitySortByNameJobShardingStrategy.sharding(Arrays.asList("host0", "host1", "host2"), new JobShardingStrategyOption("1", 2, Collections.<Integer, String>emptyMap())), is(expected));
+    }
+
+    @Test
+    public void assertshardingByDesc() {
+        Map<String, List<Integer>> expected = new LinkedHashMap<>(3);
+        expected.put("host2", Arrays.asList(0));
+        expected.put("host1", Arrays.asList(1));
+        expected.put("host0", Collections.<Integer>emptyList());
+        assertThat(
+                odevitySortByNameJobShardingStrategy.sharding(Arrays.asList("host0", "host1", "host2"), new JobShardingStrategyOption("0", 2, Collections.<Integer, String>emptyMap())), is(expected));
+    }
+}