refactor the codes related to DataSourceSelector

src/main/java/com/alibaba/druid/pool/ha/HighAvailableDataSource.java

@@ -167,11 +167,9 @@ public class HighAvailableDataSource extends WrapperAdapter implements DataSourc
     }
 
     public void setSelector(String name) {
-        if (name != null && this.selector != null && this.selector.isSame(name)) {
-            return;
-        }
         DataSourceSelector selector = DataSourceSelectorFactory.getSelector(name, this);
         if (selector != null) {
+            selector.init();
             setDataSourceSelector(selector);
         }
     }

src/main/java/com/alibaba/druid/pool/ha/selector/DataSourceSelector.java

@@ -27,7 +27,6 @@ import java.util.Map;
 public interface DataSourceSelector {
     DataSource get();
     void setTarget(String name);
-    boolean isSame(String name);
     String getName();
     void init();
 }

src/main/java/com/alibaba/druid/pool/ha/selector/DataSourceSelectorEnum.java

@@ -0,0 +1,53 @@
+package com.alibaba.druid.pool.ha.selector;
+
+import com.alibaba.druid.pool.ha.HighAvailableDataSource;
+import com.alibaba.druid.support.logging.Log;
+import com.alibaba.druid.support.logging.LogFactory;
+
+/**
+ * An enum holding the names and classes of DataSourceSelector.
+ *
+ * @author DigitalSonic
+ */
+public enum DataSourceSelectorEnum {
+    BY_NAME("byName", NamedDataSourceSelector.class),
+    RANDOM("random", RandomDataSourceSelector.class),
+    STICKY_RANDOM("stickyRandom", StickyRandomDataSourceSelector.class);
+
+    private final static Log LOG = LogFactory.getLog(DataSourceSelectorEnum.class);
+    private String name;
+    private Class<? extends DataSourceSelector> clazz;
+
+    DataSourceSelectorEnum(String name, Class<? extends DataSourceSelector> clazz) {
+        this.name = name;
+        this.clazz = clazz;
+    }
+
+    /**
+     * Create a new instance of the DataSourceSelector represented by this enum.
+     *
+     * @return null if dataSource is not given or exception occurred while creating new instance
+     */
+    public DataSourceSelector newInstance(HighAvailableDataSource dataSource) {
+        if (dataSource == null) {
+            LOG.warn("You should provide an instance of HighAvailableDataSource!");
+            return null;
+        }
+
+        DataSourceSelector selector = null;
+        try {
+            selector = clazz.getDeclaredConstructor(HighAvailableDataSource.class).newInstance(dataSource);
+        } catch (Exception e) {
+            LOG.error("Can not create new instance of " + clazz.getName(), e);
+        }
+        return selector;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public Class<? extends DataSourceSelector> getClazz() {
+        return clazz;
+    }
+}

src/main/java/com/alibaba/druid/pool/ha/selector/DataSourceSelectorFactory.java

@@ -23,11 +23,16 @@ import com.alibaba.druid.pool.ha.HighAvailableDataSource;
  * @author DigitalSonic
  */
 public class DataSourceSelectorFactory {
+    /**
+     * Get a new instance of the given selector name.
+     *
+     * @return null if the given name do not represent a DataSourceSelector
+     */
     public static DataSourceSelector getSelector(String name, HighAvailableDataSource highAvailableDataSource) {
-        if ("random".equalsIgnoreCase(name)) {
-            return new RandomDataSourceSelector(highAvailableDataSource);
-        } else if ("byName".equalsIgnoreCase(name)) {
-            return new NamedDataSourceSelector(highAvailableDataSource);
+        for (DataSourceSelectorEnum e : DataSourceSelectorEnum.values()) {
+            if (e.getName().equalsIgnoreCase(name)) {
+                return e.newInstance(highAvailableDataSource);
+            }
         }
         return null;
     }

src/main/java/com/alibaba/druid/pool/ha/selector/NamedDataSourceSelector.java

@@ -39,14 +39,9 @@ public class NamedDataSourceSelector implements DataSourceSelector {
     public void init() {
     }
 
-    @Override
-    public boolean isSame(String name) {
-        return getName().equalsIgnoreCase(name);
-    }
-
     @Override
     public String getName() {
-        return "byName";
+        return DataSourceSelectorEnum.BY_NAME.getName();
     }
 
     @Override

src/main/java/com/alibaba/druid/pool/ha/selector/RandomDataSourceSelector.java

@@ -74,14 +74,9 @@ public class RandomDataSourceSelector implements DataSourceSelector {
         }
     }
 
-    @Override
-    public boolean isSame(String name) {
-        return getName().equalsIgnoreCase(name);
-    }
-
     @Override
     public String getName() {
-        return "random";
+        return DataSourceSelectorEnum.RANDOM.getName();
     }
 
     @Override

src/main/java/com/alibaba/druid/pool/ha/selector/StickyRandomDataSourceSelector.java

@@ -25,6 +25,11 @@ public class StickyRandomDataSourceSelector extends RandomDataSourceSelector {
         super(highAvailableDataSource);
     }
 
+    @Override
+    public String getName() {
+        return DataSourceSelectorEnum.STICKY_RANDOM.getName();
+    }
+
     @Override
     public DataSource get() {
         StickyDataSourceHolder holder = holders.get();