refactoring application express - amazon web...

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Refactoring

Application Express Greg Jarmiolowski

SQLPrompt LLC

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Refactoring Application

Express

• “Too often the design is determined by the

first way everyone agrees it would work” Refactoring SQL Applications, Stéphan Faroult

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Refactoring Application

Express • What is Refactoring

• Refactoring Goals and Focus Areas

• APEX Focus Areas for Refactoring

• Finding What to Refactor

• Strategies and Challenges

• Process Overview

• Example Refactorings

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What is Refactoring

• Stepwise Refinement

• Not just tuning

• Not intended to provide new functionality

BUT

• It can lay groundwork for new functionality

• Evolution = Adapt or Die

“An effective architecture is one in which the most

likely changes are also the easiest to make.”

Software architecture in practice, Len Bass

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What is Refactoring in APEX • In APEX code is organized within a

framework

• Rewriting code goes hand in hand with

reorganizing the application

• APEX architecture informs choices

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If it ain’t broke…Why

Refactor Immediate Needs

• Security

• Performance

• Simplify

maintenance

• Scalability

• Data integrity

Future Goals

• Extend functionality

• UI Changes – AJAX ~80% of effort in systems occurs after

deployment

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Refactoring Goals

• Simplify

• Enhance performance

• Take advantage of new features

• Enhance security

• Scalability

• Reusability – Decoupling

• Specific vs. Generic

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Coding Practice Goals

• Reduce

– Redundant Code

– Dynamic SQL

– HTML in SQL and PL/SQL

• Small Code Units

• Stored Object Names

• SPODIFICATION

• Adopt a Meta Data Mindset

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Goals and Strategies

Goal Strategy

Performance Inter-element Communication

Modifiability Element Responsibilities

Security Inter-Element Communication

Scalability Localization of Resources

Ability to Subset Inter-Element Usage

Reusability Inter-Element Coupling Source: Carnegie Mellon Software Engineering Institute

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Simplification

Look for opportunities to SPODIFY

• Conditions

• Application Items

• Application Computations

• Application Processes

• Report SQL

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Performance

• Caching

– Region Cache

– SQL Cache Hint (11g)

– Function Result Cache (11g)

• Statement Tuning

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Take Advantage of New

Features Take advantage of new features in APEX

• WWV_FLOW_ASSERT

• APEX_UTIL.JSON_FROM_XX

• JavaScript APIs (apex_ns_3_1.js)

Prepare for new features in Application

• Data Access Layer API

• Application Processes

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Security

• SQL Injection

• VPD

• LDAP Integration

• Single Sign On

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Scalability Closely related to performance

• Localization of Resources

• Session State Data

• PPR/Cascading LOVs

• Use of Static Files

– one big file vs several smaller ones

– store static files outside of DB

• Reduce Network Trips

• Reduce Individual DB Reads

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Reusability

Decoupling

• Stored predicates

• Rules Manager/Expression Filter

• Queues and Jobs

• APIs encapsulating tables

• Web Services

• Workflow

• AJAX – URI dependence

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Decoupling - Rules

Manager/Expression Filter

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Specific vs. Generic

• Generalization

– Adds flexibility

– Increases centralization

• Specificity

– Can enhance performance

– Can ease troubleshooting

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Refactoring APEX

How can refactoring be applied to APEX?

• Examine APEX architecture

• Look for crossover functionality

• Look for opportunities to SPODIFY

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APEX Architecture

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Refactoring APEX

• Explore the Architecture

• Look for crossover functionality

• Use APEX views and application

reports

• Look for side effects

• Consider page lifecycle

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APEX Refactorings

• Items – Page, App, Temp

• Conditions

• Processes – Auto vs. PL/SQL

• Validations

• Branches

• Computations

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APEX Refactorings

• Reports

• Regions – HTP vs. Template

• JavaScript - AJAX

• Globalization

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APEX Refactorings

• Items – Page, App, Temporary

– Replacing page items with

Application Items

– Replacing page items in AJAX calls

with temporary items

• addGlobals()

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APEX Refactorings

Conditions

• Conditions are everywhere

• Perfect for centralizing with boolean

functions

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APEX Refactorings

Processes – Auto vs. PL/SQL

• Automatic DML and Row Fetch

– Very flexible

– Built-in optimistic locking

– Item to column mapping

– Lacks logging

– No control over errors

– Auto row fetched data not persisted* *http://c2anton.blogspot.com/2008/12/oracle-application-express-apex-three.html

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APEX Refactorings

Validations

• Ordering and short circuiting

• Reduce redundancy

• Not much crossover

• Extract logic into computation

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APEX Refactorings

Branches

• Use of ITEM vs Page number

– App Level Item vs Page Level

• New set session state option

• Ordering and short circuiting

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APEX Refactorings

Computations

• Reduce redundancy with a process

• Combine calls to the same table

– Set values in a process

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APEX Refactorings

Reports

• Replace dynamic SQL source

• Move HTML to column attributes and templates

• Simplify SQL with DB view

• Reusable predicates

• SQL calculated attributes

• APEX_COLLECTION

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APEX Refactorings

Regions

• HTP vs. Template

• Go beyond HTP.P

– Htp.anchor

– Htp.tablexxx

• APEX_ITEM – Updatable Report

• Translatable text

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APEX Refactorings

JavaScript – AJAX

• $ functions

• apex.ajax.ondemand

• AddArrayItems()

• AddPageItems()

• APEX_UTIL.JSON_FROM_SQL

• $d_LOV_from_JSON

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AJAX – URL Decoupling $a_report() - APEX PPR

pagination and

sorting function var l_URL =

'p='+$v('pFlowId')+':'+$v('pFlowStepId')+':'+$v('pInstance')+':FLOW_PPR_OUTPUT_R'+pId+'_';

… var ajax = new

htmldb_Get(null,null,null,null,null,'f',l_URL);

var gReturn = ajax.get();

f?p wwv_flow.show

App p_flow_id

Page p_flow_step_id

Session p_instance

Request p_request

Debug p_debug

Clear Cache p_clear_cache

Item Names p_arg_names

Item Values p_arg_values

PrinterFriendly p_printer_friendly

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APEX Refactorings

Globalization

• APEX_LANG

• Text Messages

– Shared Items -> Globalization

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Finding What to Refactor

• Beauty of APEX is the metadata

• APEX Component Reports

• APEX Views

• Object Dependencies

• Page “Referenced” View

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Hack the Object Depenendencies

Report

APEX_030200.wwv_flow_theme_files.find_obj

ect_dependencies

(p_flow_id=>:P1_APP_ID, p_page_id=>null);

• Need to grant rights to package

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select SEQ_ID AS ORDER_SEQ

, C001 AS schema_name

, C002 AS object_name

, C003 AS object_type

, C004 AS component_name

, C005 AS page_number

, C006 AS component_id

, C007 AS component_source

, C008 AS app_id

, C009 AS bound_items

, C010 AS component_type

, C011 AS component_source_type

from htmldb_collections

where c008 = :P1_APP_ID

and c002 <> 'PLITBLM'

and collection_name = 'ALL_DEPENDENCIES'

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Strategies

• Decide goals

• Determine scope

• Choose methods

• Create plan

• Test

• Document

• Release

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Strategies

Important Considerations

• System owner needs

• System owner capabilities

• Future changes and growth

• System owner buy in

“Every design decision comes down to cost,

benefit, and risk” The Data Model Resource Book - Volume 3, Len Silverston

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Strategies

System Owner Considerations

• Capabilities and capacity

• Complexity of resultant architecture

• Maintenance of resultant system

• Administration of resultant system

New processes, scheduled jobs

• Exception reporting

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Strategies

Future changes and growth

• How far do you go in anticipating the

progression of needs

• Does the system require more or less

flexibility in design

• Consider reusing or integrating subsets

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Strategies

Getting Buy In

• Original developer objections

• Time vs. Benefit

• Low Hanging Fruit

• Don’t estimate performance gains

• Prove inefficiencies

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Strategies

• Smaller changes are easier

• Break your work into smaller tasks

• Determine scope of changes

• The greater the coupling the harder the

refactoring

• Track changes carefully

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Strategies

Measuring your work

• How will you measure progress?

• What metrics go with your goals?

• Can you build instrumentation from your

analysis tools?

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Process Overview

• Determine refactoring(s) needed

• Choose the method(s)

• Determine the scope

• Create a new version with changes

• Test

• Document

• Release

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Example Refactorings

Add a column to the database

• Add column to db

• Add item to page

• Set the db column attributes - Auto Fetch

and Auto DML

• OR

• Add column to fetch or calculation

• Add column to DML process

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Replace SQL Exists condition with function

• SQL Conditions might seem innocuous in

the beginning but once your data grows

you might begin to see a performance hit

• If this filtered on an un-indexed column or

it includes a function call performance can

suffer

• Conditionals are often redundant

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Replace condition with authorization scheme

• If the condition relies on user dependent

attributes alone it is a good candidate for

an authorization scheme

• Probably an even better candidate for a

stored function

• An even better candidate for 11g Function

Result Cache

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Replace page process with on demand

application process

• May entail the creation of app items

• New app items need to have values set

• Extends possibilities for using AJAX

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Replace multiple branches with process to

set target page and branch to it

• May reduce redundant calls to functions

within branch conditions

• Good way to reduce function and/or query

based conditions

• Puts page branch logic in one block

• Eliminates the problem of a branch

reordering causing unexpected results

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Example Refactorings Replace Dynamic SQL with Static SQL

• Variable column lists can be made

conditional in the report attributes

• Variable table lists might indicate a bigger

problem with your design

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Example Refactorings Replace Dynamic SQL with Static SQL

• Consider the use of CASE for nested conditionals

• Think beyond “this column equals that”

• Case construct allows nested conditions –

if this is true then check these other things

• Put null conditions first to take advantage

of short-circuit evaluation

• Order conditions from most to least true

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Example Refactorings Example using CASE for where conditions SELECT *

FROM my_table

WHERE 1 = CASE

WHEN :G_SEC_LEV < 3 AND :G_FACILITY_ID = 0 THEN

CASE WHEN region_id = :G_REGION_ID THEN 1

ELSE 0 END

WHEN :G_SEC_LEV < 3 AND :G_FACILITY_ID != 0 THEN

CASE WHEN facility_id = :G_FACILITY_ID THEN 1

ELSE 0 END

WHEN :P69_REGION_ID != 0 THEN

CASE WHEN region_id = :G_REGION_ID THEN 1

ELSE 0 END

ELSE 1

END

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Example Refactorings Example using CASE for columns SELECT CASE

WHEN INSTR(':' || sec_lev || ':'

, ':' || :G_SEC_LEV || ':')>0

THEN

CASE WHEN next_sec_lev IS NOT NULL

THEN

'<a href="#" onClick="push(' || g.grid ||

'); return false;">PUSH</a>'

WHEN next_sec_lev IS NULL

THEN

'<a

href="f?p=&APP_ID.:71:&APP_SESSION.:::71:P71_GRID:

' || g.grid || '">Submit</a>'

END AS push_link

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Example Refactorings CASE statement constructs

Given mutually exclusive conditions a-d within 100 records

The ordering of the evaluation affects the total number of evaluations

CONDITION TRUE FALSE # EVALS

a 10 90 100

b 20 80 90

c 30 70 70

d 40 60 40

total records -> 100 300

CONDITION TRUE FALSE # EVALS

d 40 60 100

c 30 70 60

b 20 80 30

a 10 90 10

total records -> 100 200

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Example Refactorings Replace Automated Row Fetch with PL/SQL

expression

• Automated Row Fetch doesn’t persist session state

• No data is not an error

• Consider using record types FUNCTION get_emp(empid IN NUMBER)

RETURN employee%ROWTYPE;

DECLARE

emp_rec employee%ROWTYPE;

BEGIN

emp_rec := get_emp(:PX_EMPID);

:PX_emp_lname := emp_rec.lname;

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Example Refactorings Replace Automatic DML with PL/SQL

• Allows for custom error handling

• Consider (again) using record types PROCEDURE update_emp(empid IN employee%ROWTYPE);

DECLARE

emp_rec employee%ROWTYPE;

BEGIN

emp_rec.emp_id : = :PX_EMPID;

emp_rec.lname := :PX_EMP_LNAME;

…

update_emp(emp_rec);

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Rewriting Conditions

• Conditions are everywhere

• Reduce redundancy

• Reduce use of session state (items)

• May need to find PL/SQL equivalents for

unique condition types

– Current Page = Page Submitted

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• APEX_APPLICATION_PAGE_VAL

• APEX_APPLICATION_PARENT_TABS

• APEX_APPLICATION_PROCESSES

• APEX_APPLICATION_SHORTCUTS

• APEX_APPLICATION_TABS

• WWV_FLOW_LIST_ITEMS

• WWV_FLOW_MENU_OPTIONS

• WWV_FLOW_PAGE_PLUGS

• WWV_FLOW_REGION_REPORT_COLUMN

• WWV_FLOW_REGION_REPORT_FILTER

• WWV_FLOW_STEPS (Cache condition)

• WWV_FLOW_STEP_BRANCHES

• WWV_FLOW_STEP_BUTTONS

• WWV_FLOW_STEP_VALIDATIONS

• WWV_FLOW_TABS

• WWV_FLOW_TOPLEVEL_TABS

• APEX_APPLICATION_BC_ENTRIES

• APEX_APPLICATION_COMPUTATIONS

• APEX_APPLICATION_LIST_ENTRIES

• APEX_APPLICATION_LOV_ENTRIES

• APEX_APPLICATION_NAV_BAR

• APEX_APPLICATION_PAGES

• APEX_APPLICATION_PAGE_BRANCHES

• APEX_APPLICATION_PAGE_BUTTONS

• APEX_APPLICATION_PAGE_COMP

• APEX_APPLICATION_PAGE_IR

• APEX_APPLICATION_PAGE_IR_COL

• APEX_APPLICATION_PAGE_IR_COND

• APEX_APPLICATION_PAGE_ITEMS

• APEX_APPLICATION_PAGE_PROC

• APEX_APPLICATION_PAGE_REGIONS

• APEX_APPLICATION_PAGE_RPT_COLS

Conditions are everywhere

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Replacing Conditions with Authorizations

• Can be evaluated per session or page view

• Can be subscribed to for sharing across

applications

• Can be reused in Conditions apex_util.public_check_authorization

(‘AUTHORIZATION_SCHEME_NAME’)

• Can be reset as needed (all or nothing) apex_util.reset_authorizations

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Replacing Conditions with Authorizations • Available for the following components

– Application

– Computation

– Navigation Bar

– List Items

– Breadcrumb Entry

– Region

– Process (page and app level)

– Report Column

– Page

– Branch

– Button

– Item

– Validation

– Tab

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Replacing Item Level LOV with shared LOV

• WWV_FLOW_STEP_ITEMS.LOV

Shows LOVs defined at item level

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Suggested Reading

Refactoring Databases:

Evolutionary Database

Design

Scott W. Ambler and

Pramodkumar J. Sadalage

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Suggested Reading

Refactoring SQL

Applications

Stephane Faroult and

Pascal L'Hermite

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Suggested Reading

Oracle PL/SQL Best

Practices

Steven Feuerstein

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Refactoring

Application Express Greg Jarmiolowski

SQLPrompt LLC

refactoring application express - amazon web...

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