Let us take a look at steps 2 and 3 of the 'execute' method.
// Step 2: Allocate a 'Statement' object in the Connection
Statement stmt = conn.createStatement();
// Step 3: Execute a SQL SELECT query. The query result is returned in a 'ResultSet' object.
String strSelect = "select title, author, price, qty from books"; // <== 'books' is table name
ResultSet rset = stmt.executeQuery(strSelect);
As we described in Step08, the database name and user ID have been externalized into IIPs. The table name (books) is in the select statement above, but should also be externalized, so we will append that to the database name IIP, separated by an exclamation mark, and ReadJDBC will be modified to split this IIP for the two usages. See
For now, we will still list the table rows (on the console), but it doesn't make sense to turn Book into a Java String, as we don't know what the next process in the network will be, plus we will probably want to update a table or tables on the output end, which will need "book"s unchanged, so the Book object should be output as is.
WriteToConsole cannot accept "book" objects as input, so we will add a process to turn Book into String, as shown in the diagram below. We could build an ad hoc component to fill this gap, but in fact we can use reflection to build a generalized component, which not only displays the fields, but also shows their names as well, plus the class name.
We have built a component called WriteObjectsToConsole.java which implements the latter suggestion - it took about 20 minutes to write! It can be found in https://github.com/jpaulm/fbp-etl/blob/master/src/main/java/com/jpaulmorrison/jdbcstuff/core/components/WriteObjectsToConsole.java, and replaces WriteToConsole in the diagram. The output of ReadJDBC.java can no longer assume Java Strings, so this restriction has been removed from the @OutPort annotation.
WriteObjectsToConsole also outputs incoming IPs if an output port is connected.
Here is the updated diagram:
Here is a sample of the output from WriteObjectsToConsole.java:
