support reset filters

src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java

@@ -1158,6 +1158,14 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
     }
 
     public void setFilters(String filters) throws SQLException {
+        if (filters != null && filters.startsWith("!")) {
+            filters = filters.substring(1);
+            this.clearFilters();
+        }
+        this.addFilters(filters);
+    }
+    
+    public void addFilters(String filters) throws SQLException {
         if (filters == null || filters.length() == 0) {
             return;
         }
@@ -1166,7 +1174,7 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
 
         for (String item : filterArray) {
             FilterManager.loadFilter(this.filters, item);
-        }
+        }        
     }
     
     public void clearFilters() {

src/test/java/com/alibaba/druid/bvt/filter/ClearFilterTest.java

@@ -0,0 +1,22 @@
+package com.alibaba.druid.bvt.filter;
+
+import junit.framework.TestCase;
+
+import org.junit.Assert;
+
+import com.alibaba.druid.filter.stat.StatFilter;
+import com.alibaba.druid.pool.DruidDataSource;
+
+
+public class ClearFilterTest extends TestCase {
+    public void test_filters() throws Exception {
+        DruidDataSource dataSource = new DruidDataSource();
+        Assert.assertEquals(0, dataSource.getProxyFilters().size());
+        dataSource.setFilters("encoding");
+        Assert.assertEquals(1, dataSource.getProxyFilters().size());
+        dataSource.setFilters("!stat");
+        Assert.assertEquals(1, dataSource.getProxyFilters().size());
+        Assert.assertEquals(StatFilter.class.getName(), dataSource.getFilterClassNames().get(0));
+        dataSource.close();
+    }
+}

src/test/java/com/alibaba/druid/pool/MemTest.java

@@ -0,0 +1,57 @@
+package com.alibaba.druid.pool;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.util.List;
+
+import com.alibaba.druid.sql.ast.SQLStatement;
+import com.alibaba.druid.sql.parser.SQLParserUtils;
+import com.alibaba.druid.sql.parser.SQLStatementParser;
+import com.alibaba.druid.sql.visitor.ParameterizedOutputVisitorUtils;
+import com.alibaba.druid.sql.visitor.SQLASTOutputVisitor;
+
+public class MemTest {
+
+    public static void main(String[] args) throws Exception {
+//        DruidDataSource dataSource = new DruidDataSource();
+//        dataSource.setUrl("jdbc:mock:xxx");
+//        dataSource.setInitialSize(1);
+//        dataSource.setDbType("mysql");
+//        dataSource.setFilters("mergeStat");
+        // dataSource.setPoolPreparedStatements(true);
+        // dataSource.setMaxOpenPreparedStatements(50);
+
+        // for (int i = 1000; i < 2000; ++i) {
+        // String tableName = "t" + i;
+        // String sql = "select * from " + tableName + " where " + tableName + ".id = " + i;
+        // Connection conn = dataSource.getConnection();
+        //
+        // PreparedStatement stmt = conn.prepareStatement(sql);
+        // stmt.execute();
+        // stmt.close();
+        //
+        // conn.close();
+        // }
+
+        // Connection conn = dataSource.getConnection();
+        //
+        String sql = "SELECT UMID, HWID, MAC, GUID, RID , GMT_CREATE, GMT_MODIFIED FROM umid_rid " + //
+                     "WHERE RID = ? " + //
+                     "LIMIT 10";
+        // PreparedStatement stmt = conn.prepareStatement(sql);
+        // stmt.execute();
+
+        SQLStatementParser parser = SQLParserUtils.createSQLStatementParser(sql, "mysql");
+        List<SQLStatement> statementList = parser.parseStatementList();
+
+        SQLStatement stmt = statementList.get(0);
+
+        StringBuilder out = new StringBuilder();
+        SQLASTOutputVisitor visitor = ParameterizedOutputVisitorUtils.createParameterizedOutputVisitor(out, "mysql");
+        stmt.accept(visitor);
+
+        Thread.sleep(1000 * 1000);
+//        dataSource.close();
+    }
+}