refactor

src/main/java/com/alibaba/druid/mapping/spi/MySqlMappingProvider.java

@@ -0,0 +1,46 @@
+package com.alibaba.druid.mapping.spi;
+
+import com.alibaba.druid.mapping.MappingEngine;
+import com.alibaba.druid.sql.ast.expr.SQLNumberExpr;
+import com.alibaba.druid.sql.ast.statement.SQLSelectQueryBlock;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlSelectQueryBlock;
+import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlSelectQueryBlock.Limit;
+import com.alibaba.druid.sql.dialect.mysql.parser.MySqlSelectParser;
+import com.alibaba.druid.sql.dialect.mysql.visitor.MySqlOutputVisitor;
+import com.alibaba.druid.sql.visitor.SQLASTOutputVisitor;
+
+public class MySqlMappingProvider implements MappingProvider {
+
+    @Override
+    public MappingVisitor createMappingVisitor(MappingEngine engine) {
+        return new MySqlMappingVisitor(engine.getEntities());
+    }
+
+    @Override
+    public SQLASTOutputVisitor createOutputVisitor(MappingEngine engine, Appendable out) {
+        return new MySqlOutputVisitor(out);
+    }
+
+    public SQLSelectQueryBlock explainToSQLObject(MappingEngine engine, String sql) {
+        MySqlSelectParser selectParser = new MySqlSelectParser(sql);
+        MySqlSelectQueryBlock query = (MySqlSelectQueryBlock) selectParser.query();
+
+        Integer maxLimit = engine.getMaxLimit();
+
+        if (maxLimit != null) {
+            if (query.getLimit() == null) {
+                Limit limit = new Limit();
+                limit.setRowCount(new SQLNumberExpr(maxLimit));
+                query.setLimit(limit);
+            } else {
+                SQLNumberExpr rowCountExpr = (SQLNumberExpr) query.getLimit().getRowCount();
+                int rowCount = rowCountExpr.getNumber().intValue();
+                if (rowCount > maxLimit.intValue()) {
+                    rowCountExpr.setNumber(maxLimit);
+                }
+            }
+        }
+
+        return query;
+    }
+}