Creating RESTful API's with the APEX Listener

In REST you model the resources, not the actions. So you define a GET /apex/oow13/hr/employees instead of a GET /apex/oow13/GetAllEmployees. With REST you have six methods (with the most common associated database actions: GET (select), HEAD (select), OPTIONS (to get a list of methods supported by the resource), PUT (merge or update), DELETE (delete), POST (insert).

You can manage the REST resources from either within SQL Developer or APEX. Within SQL Developer the resources are grouped into Modules (like PL/SQL packages) with a URI prefix (like /hr) and within that Resource Templates.

As an example you can define a GET request ( select * from emp where empno = :id ), then the URI Template of the resource will be something like employees/{id}. When you call the URL (like http://localhost:8888/apex/oow13/hr/employees/12345), this will result in a JSON string (or XML or CSV) containing the employee data of employee 12345.

Within a query you can use "special" columns - starting with a $ - that will return a hyperlink within the JSON object.

The listener supports CORS (Cross Origin Resource Sharing) for all public services. So you're not restricted to using URI's within the same domain and can create mashups using data from different domains. Protected resources are not CORS enabled by default, however you can specify a whitelist of origins that are allowed to call that service.

In SQL Developer you can also assign "Privileges" for mehods - so you can secure your DELETE operations from your SELECT operation. The autorization is implemented as an "oauth2" call. See the APEX Listener documentation for more details on that.

Comments

Filtering in the APEX Interactive Grid

Remember Oracle Forms? One of the nice features of Forms was the use of GLOBAL items. More or less comparable to Application Items in APEX. These GLOBALS where often used to pre-query data. For example you queried Employee 200 in Form A, then opened Form B and on opening that Form the Employee field is filled with that (GLOBAL) value of 200 and the query was executed. So without additional keys strokes or entering data, when switching to another Form a user would immediately see the data in the same context. And they loved that. In APEX you can create a similar experience using Application Items (or an Item on the Global Page) for Classic Reports (by setting a Default Value to a Search Item) and Interactive Reports (using the APEX_IR.ADD_FILTER procedure). But what about the Interactive Grid? There is no APEX_IG package ... so the first thing we have to figure out is how can we set a filter programmatically? Start with creating an Interactive Grid based upon the good old Employ

apex_application.g_f0x array processing in Oracle 12

If you created your own "updatable reports" or your custom version of tabular forms in Oracle Application Express, you'll end up with a query that looks similar to this one: then you disable the " Escape special characters " property and the result is an updatable multirecord form. That was easy, right? But now we need to process the changes in the Ename column when the form is submitted, but only if the checkbox is checked. All the columns are submitted as separated arrays, named apex_application.g_f0x - where the "x" is the value of the "p_idx" parameter you specified in the apex_item calls. So we have apex_application.g_f01, g_f02 and g_f03. But then you discover APEX has the oddity that the "checkbox" array only contains values for the checked rows. Thus if you just check "Jones", the length of g_f02 is 1 and it contains only the empno of Jones - while the other two arrays will contain all (14) rows. So for

Stop using validations for checking constraints !

If you run your APEX application - like a Form based on the EMP table - and test if you can change the value of Department to something else then the standard values of 10, 20, 30 or 40, you'll get a nice error message like this: But it isn't really nice, is it? So what do a lot of developers do? They create a validation (just) in order to show a nicer, better worded, error message like "This is not a valid department". And what you then just did is writing code twice : Once in the database as a (foreign key) check constraint and once as a sql statement in your validation. And we all know : writing code twice is usually not a good idea - and executing the same query twice is not enhancing your performance! So how can we transform that ugly error message into something nice? By combining two APEX features: the Error Handling Function and the Text Messages! Start with copying the example of an Error Handling Function from the APEX documentation. Create this function

Roels Blog

Search This Blog