Extract list of all fields from Page Layout

I got requirement from my team where they wanted list of fields which are used or placed on page layout.  They wanted to extract fields without any App Exchange product or tool.

For this requirement i have used Metadata API and Tooling API in apex to get list of all field by specifying page layout.  Below are steps which we have to perform for getting fields

1. Get Org objects
2. Get Layout of object
3. Get field of Page Layout
4. Show above object, layout and fields information on Lightning Web Component
5. Download fields as CSV File

1. Get Org objects

First we need list of all objects for which page layouts will be shown.  We can get complete list of objects using Describe API.  We can get standard as well custom objects of Salesforce Org.

for(Schema.SObjectType objTyp : Schema.getGlobalDescribe().Values()){
 system.debug(objTyp.getDescribe().getName());
}

2. Get Layout of object

Now we have list of all objects, let us get layouts of these object. We can get layout with specific object. We have to use Tooling API to get list of page layout for specific object.  We can use ProfileLayout object like below SOQL for getting object’s page layout.

 string sql='select Layout.Name from ProfileLayout where TableEnumOrId=\'objectName\'';

3. Get fields of Page Layout

Based on above two steps we can get fields of page layout. We can use Metadata API to get fields of any specific page layout.

string layoutName=String.format('{0}-{1}', new String[]{objectName, layout}); 
List<Metadata.Metadata> layouts = Metadata.Operations.retrieve(Metadata.MetadataType.Layout, new List<String> {layoutName});

4. Show object, layout and fields information on Lightning Web Component

Now let us use above steps to show information on Lightning Web Component. We will add two combo-box, one for displaying object name and other for layout of selected object name.

We also have to add lightning-datatable in which we will show list of all fields for selected object and layout.

5. Download fields as CSV File

We can download field information as csv or excel. We can use text/csv mime type for downloading as CSV file.

   let csvContent = "data:text/csv;charset=utf-8,";
    csvContent +="Fields,\r\n"; //header
    this.fields.forEach(function(rowArray) {
        let row = rowArray.value+",";
        csvContent += row + "\r\n";
    });

    var encodedUri = encodeURI(csvContent);
    var link = document.createElement("a");
    link.setAttribute("href", encodedUri);
    link.setAttribute("download", this.layoutName+".csv");
    document.body.appendChild(link); 
    link.click();

Important Pre-requisites

1. By default we can’t call Tooling API directly with Apex using UserInfo.getSessionId().  We have to create Connected App,  Auth Provider and Named Credential for this. Please refer blog https://salesforcecodex.com/2020/05/call-tooling-api-from-lightning-web-component/ for this. 
2. We have created named credential ToolingRest for this blog.

Complete Code:

1. Apex Code

2. Lightning Web Component

Test Page:

References:

https://developer.salesforce.com/docs/atlas.en-us.api_tooling.meta/api_tooling/

https://developer.salesforce.com/docs/atlas.en-us.api_meta.meta/api_meta/meta_intro.htm

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