What makes this sql failure in JDBC?

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Java

MySQL

The very same sql statement works fine in MySQL Workbench but fails in Java program. All I've done was setting a breakpoint before the execution of this statement in Java and paste the same statement ("select * from administrator where AdministratorID = 'Admin'") from Java to the Workbench, where showed ONE record. I surrounded the invoking with try-catch, it turned out successfully called but returned nothing (resultset.getRow() returns 0). Here is the Java code that executes the query:

public ResultSet executeQuery(String tableName, String condition) {
		String sql = "select * from " + tableName + " where " + condition;
		ResultSet rs = null;
		Connection conn = null;
		try {
			conn = getConn();
			Statement statement = conn.createStatement();
			rs = statement.executeQuery(sql);
			statement.close();
			conn.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
		return rs;
	}

And the getConn() function:

public Connection getConn() {
		Connection conn = null;
		try {
			Class.forName(name); // 指定连接类型
			String url = "jdbc:mysql://" + host + ":" + port + "/" + dbName;
			conn = DriverManager.getConnection(url, user, password); // 获取连接
		} catch (Exception e) {
			e.printStackTrace();
		}
		return conn;
	}

where name = "com.mysql.jdbc.Driver", host = "127.0.0.1", port = "3306". dbName, user and password were provided correctly.
Can anyone help tell me what went wrong?