UseHandler.java

/*
 * Copyright 1999-2012 Alibaba Group.
 * 
 * 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.
 */
package fm.liu.timo.server.handler;

import java.nio.ByteBuffer;
import java.util.Set;
import fm.liu.timo.config.ErrorCode;
import fm.liu.timo.mysql.packet.OkPacket;
import fm.liu.timo.net.handler.FrontendPrivileges;
import fm.liu.timo.server.ServerConnection;

/**
 * @author xianmao.hexm
 */
public final class UseHandler {

    public static void handle(String sql, ServerConnection c, int offset) {
        String schema = sql.substring(offset).trim();
        int length = schema.length();
        if (length > 0) {
            if (schema.charAt(0) == '`' && schema.charAt(length - 1) == '`') {
                schema = schema.substring(1, length - 2);
            }
        }

        // 表示当前连接已经指定了schema
        if (c.getDB() != null) {
            if (c.getDB().equals(schema)) {
                ByteBuffer buffer = c.allocate();
                c.write(c.writeToBuffer(OkPacket.OK, buffer));
            } else {
                c.writeErrMessage(ErrorCode.ER_DBACCESS_DENIED_ERROR,
                        "Not allowed to change the database!");
            }
            return;
        }

        // 检查schema的有效性
        FrontendPrivileges privileges = c.getPrivileges();
        if (schema == null || !privileges.schemaExists(schema)) {
            c.writeErrMessage(ErrorCode.ER_BAD_DB_ERROR, "Unknown database '" + schema + "'");
            return;
        }
        String user = c.getUser();
        if (!privileges.userExists(user, c.getHost())) {
            c.writeErrMessage(ErrorCode.ER_ACCESS_DENIED_ERROR,
                    "Access denied for user '" + c.getUser() + "'");
            return;
        }
        Set<String> schemas = privileges.getUserSchemas(user);
        if (schemas == null || schemas.size() == 0 || schemas.contains(schema)) {
            c.setDB(schema);
            ByteBuffer buffer = c.allocate();
            c.write(c.writeToBuffer(OkPacket.OK, buffer));
        } else {
            String msg =
                    "Access denied for user '" + c.getUser() + "' to database '" + schema + "'";
            c.writeErrMessage(ErrorCode.ER_DBACCESS_DENIED_ERROR, msg);
        }
    }

}