UI5 Best Practices and Coding Standards

Overview

This skill enforces UI5 development standards derived from official SAP guidelines. It covers the four critical areas: coding guidelines, tooling integration, CAP integration, and form creation rules.

1. Module Loading - CRITICAL

Never Use Global Access

NEVER access UI5 framework objects globally (e.g.,

sap.m.Button

). Always declare dependencies explicitly for asynchronous loading.

JavaScript

javascript

// ❌ WRONG - Global access
var oButton = new sap.m.Button();

// ✅ CORRECT - Explicit dependency
sap.ui.define(["sap/m/Button"], function(Button) {
    var oButton = new Button();
});

// ✅ CORRECT - Dynamic loading with sap.ui.require
sap.ui.require(["sap/m/MessageBox"], function(MessageBox) {
    MessageBox.show("Hello");
});

TypeScript

typescript

// ❌ WRONG - Global namespace
const button: sap.m.Button;

// ✅ CORRECT - Import module
import Button from "sap/m/Button";
const button: Button;

XML Views

xml

<!-- ✅ Controls are auto-loaded by tag -->
<m:Button text="Click Me"/>

<!-- ✅ For formatters/types, use core:require -->
<ObjectListItem
    core:require="{
        Currency: 'sap/ui/model/type/Currency'
    }"
    number="{
        parts: ['invoice>Price', 'view>/currency'],
        type: 'Currency'
    }"/>

Why: Ensures proper async loading, improves performance in production builds.

Reference: UI5 documentation page "Require Modules in XML View and Fragment"

2. Component Initialization

Use

sap/ui/core/ComponentSupport

for declarative initialization of the initial (root) component:

html

<!-- index.html -->
<script id="sap-ui-bootstrap"
    src="resources/sap-ui-core.js"
    data-sap-ui-on-init="module:sap/ui/core/ComponentSupport"
    data-sap-ui-async="true"
    data-sap-ui-resource-roots='{ "my.app": "./" }'>
</script>

<body class="sapUiBody">
    <div data-sap-ui-component 
         data-name="my.app" 
         data-id="container">
    </div>
</body>

Reference: UI5 documentation page "Declarative API for Initial Components"

Note: Nested components should be managed via component usages (declared in the manifest.json of the containing component)

3. Data Binding Best Practices

Always Use Built-in Data Types

ALWAYS use data binding in views to connect UI controls to data or i18n models.

Priority order:

OData types (
```
sap/ui/model/odata/type/*
```
) - Preferred
Simple types (
```
sap/ui/model/type/*
```
) - Only when no OData equivalent
Custom types - For special two-way binding scenarios or complex validation
Custom formatters - Only for unique business logic (one-way binding)

xml

<!-- ❌ WRONG - Custom formatter for standard formatting -->
<Text text="{path: 'price', formatter: '.formatCurrency'}"/>

<!-- ✅ CORRECT - Use OData type with format options -->
<Text text="{
    path: 'price',
    type: 'sap.ui.model.odata.type.Decimal',
    formatOptions: {
        style: 'currency',
        currencyCode: 'EUR'
    }
}"/>

<!-- ✅ CORRECT - Use grouping for thousands separator -->
<Text text="{
    path: 'quantity',
    type: 'sap.ui.model.odata.type.Decimal',
    formatOptions: {
        groupingEnabled: true
    }
}"/>

Common OData Types:

```
sap.ui.model.odata.type.Decimal
```
- Numbers with decimals
```
sap.ui.model.odata.type.String
```
- Text with length constraints
```
sap.ui.model.odata.type.DateTime
```
- Date and time

Common Simple Types (use only when no OData equivalent):

```
sap.ui.model.type.DateInterval
```
- Date ranges
```
sap.ui.model.type.FileSize
```
- File size formatting

Example: For number formatting with thousands separator, prefer

sap.ui.model.odata.type.Decimal

with

formatOptions: {groupingEnabled: true}

over

sap.ui.model.type.Integer

or a custom formatter.

When to Use Custom Types

Custom types are needed for special two-way binding scenarios where built-in types don't provide the required validation or conversion logic.

Example: Custom Type for Email Validation with Two-Way Binding

javascript

// controller/EmailType.js
sap.ui.define(["sap/ui/model/SimpleType"], function(SimpleType) {
    return SimpleType.extend("my.app.type.EmailType", {
        formatValue: function(oValue) {
            return oValue;
        },
        parseValue: function(oValue) {
            return oValue;
        },
        validateValue: function(oValue) {
            const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
            if (oValue && !emailRegex.test(oValue)) {
                throw new sap.ui.model.ValidateException("Invalid email format");
            }
        }
    });
});

Usage in View:

xml

<!-- ❌ WRONG - Formatter doesn't work for two-way binding validation -->
<Input value="{path: 'email', formatter: '.validateEmail'}"/>

<!-- ✅ CORRECT - Custom type enables two-way binding with validation -->
<Input 
    core:require="{EmailType: 'my/app/type/EmailType'}"
    value="{
        path: 'email',
        type: 'EmailType'
    }"/>

Why Custom Types:

✅ Two-way binding support (formatValue + parseValue + validateValue)
✅ Real-time validation as user types
✅ Model updates immediately on valid input
❌ Custom formatters only work for one-way (display) binding

Data Binding in Views

ALWAYS use data binding to connect controls to models:

xml

<!-- Property binding -->
<Input value="{/customer/name}"/>

<!-- Aggregation binding -->
<List items="{/products}">
    <StandardListItem title="{name}" description="{price}"/>
</List>

<!-- Expression binding -->
<Text text="{= ${quantity} * ${price} }" visible="{= ${stock} > 0 }"/>

4. Internationalization (i18n)

Translation Workflow Guidelines

When modifying

.properties

files, follow the appropriate workflow based on your project type:

For development and testing:

Update
```
i18n.properties
```
(base file) only
Changes will be reflected immediately for development

Production translation workflows:

SAP S/4HANA apps: NEVER manually edit localized files (
```
i18n_de.properties
```
,
```
i18n_fr.properties
```
, etc.)
- Translation is handled through SAP's internal translation process
Apps using SAP Translation Hub or Translation Export/Import (TEW): DO NOT touch localized files
- Translations are generated automatically from the base file
Manually translated apps only: Apply changes to all locale files to maintain consistency

Why: Professional translation workflows generate localized files from the base

i18n.properties

file. Manual edits to localized files will be overwritten during the translation process.

5. Security - Content Security Policy

Never Use Inline Scripts or Styles

NEVER use inline scripts or inline styles in HTML. They violate the recommended CSP settings for UI5 applications.

html

<!-- ❌ WRONG - Violates CSP -->
<script>
    alert("Hello");
</script>

<style>
    .error { color: red; }
</style>

<div style="color: red;">Styled text</div>

<!-- ✅ CORRECT - External files -->
<script src="controller/Main.controller.js"></script>
<link rel="stylesheet" href="css/style.css">

<!-- ✅ CORRECT - CSS classes -->
<div class="errorText">Styled text</div>

Requirements:

All application logic must reside in dedicated JS or TS files
All styling must reside in dedicated CSS files
Inline
```
<script>
```
tags violate CSP
Inline
```
<style>
```
tags violate CSP
Inline
```
style
```
attributes violate CSP

Reference: UI5 documentation page "Content Security Policy"

6. TypeScript Event Handling (UI5 >= 1.115.0)

Use Control-Specific Event Types

For UI5 1.115.0 and above, import and use the specific event type from the control's module.

Pattern:

<ControlName>$<EventName>Event

(notice the "Event" suffix)

typescript

// ✅ CORRECT - Import specific event type
import { Button$PressEvent } from "sap/m/Button";
import { Table$RowSelectionChangeEvent } from "sap/ui/table/Table";
import Controller from "sap/ui/core/mvc/Controller";

export default class MainController extends Controller {
    public onPress(event: Button$PressEvent): void {
        const button = event.getSource();  // Correctly typed as Button
        // ...
    }
    
    public onRowSelectionChange(event: Table$RowSelectionChangeEvent): void {
        // Correctly typed: getParameter is known and return value inferred
        const selectedContext = event.getParameter("rowContext");
        // ...
    }
}

Fallback for Older Versions

UI5 < 1.115.0: Control-specific event types are NOT available. Use the generic Event type:

typescript

import Event from "sap/ui/base/Event";
import Controller from "sap/ui/core/mvc/Controller";

export default class MainController extends Controller {
    public onPress(event: Event): void {
        // Generic Event type for UI5 < 1.115.0
        // ...
    }
}

Benefits: Static type checking and autocompletion for event parameters without manual casting.

7. MCP Tooling Integration

API Lookup

ALWAYS use the

get_api_reference

tool to get information on UI5 controls and APIs. This provides direct access to the official UI5 API Reference for the UI5 version in use.

Usage: get_api_reference with project path
Returns: Official API documentation for controls, classes, and namespaces

Code Validation

ALWAYS use the

run_ui5_linter

tool to identify issues. It detects deprecated APIs, accessibility issues, and other potential bugs.

Usage: run_ui5_linter with project path
Returns: List of issues with severity levels

Code Fixes

To apply fixes suggested by the linter:

ALWAYS confirm with the user first
Use the
```
fix
```
parameter of the
```
run_ui5_linter
```
tool
The tool automatically corrects some identified issues
Manually fix remaining issues using the context information provided

Local Server Behavior

When interacting with the UI5 CLI's development server:

CRITICAL: The server does NOT serve a default index file.

bash

# ❌ WRONG - Will not work
http://localhost:8080/

# ✅ CORRECT - Must reference files by full path
http://localhost:8080/index.html

Code Quality Checks

After making code changes, ALWAYS run the project's linter if available:

bash

npm run lint           # Standard
npm run eslint         # Alternative
eslint .               # Direct ESLint call
npm run ui5-lint       # UI5 Linter if configured
ui5lint .              # UI5 Linter if available as CLI tool

Why: Linters catch common issues before committing:

Missing imports or type errors
Formatting inconsistencies
Deprecated API usage
Code style violations

Fix all linting errors before committing.

8. CAP Integration

When creating a UI5 project within a CAP (Cloud Application Programming Model) project:

Project Location

ALWAYS create UI5 projects within the

app/

directory of the CAP project root.

cap-project/
├── app/                    # ← UI5 apps go here
│   └── my-ui5-app/
├── srv/                    # CAP services
├── db/                     # Database models
└── package.json

Service Information

Get service information:

If CDS tools are available: Use them to get definitions, services, and endpoints

If no CDS tools: Run these commands:

bash

cds compile '*'                        # Get definitions
cds compile '*' --to serviceinfo       # Get services and endpoints

Service Integration

When creating the UI5 project, ALWAYS provide:

Absolute OData V4 service URL
Target entity set

Plugin Installation

ALWAYS run in CAP project root:

bash

npm i -D cds-plugin-ui5

This plugin automatically handles serving the UI5 applications.

Running the Server

bash

# ❌ WRONG - Never run separate UI5 server
cd app/my-ui5-app
ui5 serve                    # Don't do this!
npm start                    # Don't do this!

# ✅ CORRECT - Run from CAP project root
cds watch                    # Serves both backend and UI5 apps
# or
cds run                      # Alternative command

Why: Single command serves both backend services and all UI5 applications from the same origin (

http://localhost:4004

Data Connection

NEVER configure

ui5-middleware-simpleproxy

ui5.yaml

yaml

# ❌ WRONG - No proxy needed
server:
  customMiddleware:
    - name: ui5-middleware-simpleproxy    # Don't add this!

Why:

cds watch

ensures UI and service are served from the same origin, making a proxy unnecessary.

Accessing the App

Check the CAP launch page (typically

http://localhost:4004

) for:

List of available services
Links to UI5 applications

9. Form Creation Rules

Never Use SimpleForm (Unless Explicitly Requested)

xml

<!-- ❌ AVOID - SimpleForm -->
<form:SimpleForm>
    <Label text="Name"/>
    <Input value="{name}"/>
</form:SimpleForm>

<!-- ✅ CORRECT - Use Form with ColumnLayout -->
<form:Form editable="true">
    <form:layout>
        <form:ColumnLayout
            columnsM="2"
            columnsL="3"
            columnsXL="4"/>
    </form:layout>
    <form:formContainers>
        <form:FormContainer title="Personal Data">
            <form:formElements>
                <form:FormElement label="Name">
                    <form:fields>
                        <Input value="{name}"/>
                    </form:fields>
                </form:FormElement>
            </form:formElements>
        </form:FormContainer>
    </form:formContainers>
</form:Form>

Default Column Configuration

ALWAYS use these defaults unless requested differently:

M-size: 2 columns
L-size: 3 columns
XL-size: 4 columns

Documentation References

For additional information, consult these UI5 documentation pages:

"Require Modules in XML View and Fragment"
"Declarative API for Initial Components"
"Content Security Policy"
Official UI5 API Reference (use
```
get_api_reference
```
tool)

ui5-best-practices

NPX Install

Tags

SKILL.md Content

UI5 Best Practices and Coding Standards

Overview

1. Module Loading - CRITICAL

Never Use Global Access

JavaScript

TypeScript

XML Views

2. Component Initialization

3. Data Binding Best Practices

Always Use Built-in Data Types

When to Use Custom Types

Data Binding in Views

4. Internationalization (i18n)

Translation Workflow Guidelines

5. Security - Content Security Policy

Never Use Inline Scripts or Styles

6. TypeScript Event Handling (UI5 >= 1.115.0)

Use Control-Specific Event Types

Fallback for Older Versions

7. MCP Tooling Integration

API Lookup

Code Validation

Code Fixes

Local Server Behavior

Code Quality Checks

8. CAP Integration

Project Location

Service Information

Service Integration

Plugin Installation

Running the Server

Data Connection

Accessing the App

9. Form Creation Rules

Never Use SimpleForm (Unless Explicitly Requested)

Default Column Configuration

Documentation References