bug fixed for mapping && remove warnings

src/main/java/com/alibaba/druid/mapping/MappingContext.java

@@ -0,0 +1,36 @@
+package com.alibaba.druid.mapping;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class MappingContext {
+
+    private List<Object> parameters;
+
+    private boolean      generateAlias = false;
+
+    public MappingContext(){
+        this(new ArrayList<Object>());
+    }
+
+    public MappingContext(List<Object> parameters){
+        this.parameters = parameters;
+    }
+
+    public List<Object> getParameters() {
+        return parameters;
+    }
+
+    public void setParameters(List<Object> parameters) {
+        this.parameters = parameters;
+    }
+
+    public boolean isGenerateAlias() {
+        return generateAlias;
+    }
+
+    public void setGenerateAlias(boolean generateAlias) {
+        this.generateAlias = generateAlias;
+    }
+
+}