Displaying CLOB Contents in Oracle Apex

April 26, 2023December 14, 2019 by Vinish Kapoor

In this tutorial, you will learn how to display CLOB contents in Oracle Apex. The Character large object (CLOB) is a collection of character data in the database. Usually stores the large data like HTML, XML, CSV, Plain Text, Word and Excel file, etc. Here I am giving an example to display the CLOB contents into a region in Oracle Apex. Follow these steps:

Steps to Display CLOB Contents in Oracle Apex Page Region

To demonstrate the following example, I am using the SUPPLIERS table. To test this example in your Oracle environment, create the table as shown below:

1. Create the following table with CLOB column

Create TABLE SUPPLIERS (
SUPPLIER_ID INTEGER,
SUPPLIER_NAME VARCHAR2(100),
ADDRESS VARCHAR2(100),
PHONE VARCHAR2(40),
AGREEMENT_DOC CLOB,
MIMETYPE VARCHAR2(1000)
)
/

Insert some data in the above table with some CLOB data also and provide the correct MIME TYPE for each type of CLOB content. For example:

For HTML Data provide mime type text/html.
For CSV Data > text/csv
For Plain Text > text/plain
Word file > msword
Excel file > ms-excel

Below is the screenshot of the data:

2. Create an Interactive Report in Oracle Apex

Create an interactive report in Oracle Apex based on the above table. Use the following query to display all the data except the CLOB column:

select 
       SUPPLIER_ID,
       SUPPLIER_NAME,
       ADDRESS,
       PHONE,
       'Preview' Preview
  from SUPPLIERS

Below is the screenshot for the report settings:

3. Create a Page Item

Do the right-click on the interactive report region and from the shortcut menu select Create Page Item. Set the name as SUPPLIER_ID, my page number is 2 so the page item name is P2_SUPPLIER_ID.

4. Create a Static Content Region

Do the right-click on the content region and from the shortcut menu select Create Region and set the following properties:

Title: Preview
Type: Static Content
Start New Row: No
Advanced > Static ID: preview1
Source > Text: Add the following code:

<p align="center">
<iframe id="myFrame1" src="" width="99%" height="750">
</iframe>
</p>

Below is the screenshot for the above settings:

Save the changes for the page.

5. Create an Application Process

Now create an application process in Oracle Apex. To do this, click on the Shared Components > Application Process and then click on the Create button. The following window will appear:

Specify the name as preview_clob_data and select the Ajax Callback for the Point drop-down.

Then click on the Next button. And in the next screen paste the following PL/SQL code, as shown below:

DECLARE
  vClob CLOB;
  vblob blob;
  vmimetype varchar2(1000);
    L_DEST_OFFSET    INTEGER := 1;
    L_SRC_OFFSET     INTEGER := 1;
    L_LANG_CONTEXT   INTEGER := DBMS_LOB.DEFAULT_LANG_CTX;
    L_WARNING        INTEGER;
    L_LENGTH         INTEGER;
BEGIN

 Dbms_Lob.Createtemporary(Lob_Loc => vclob,
                                   Cache   => TRUE,
                                   Dur     => Dbms_Lob.Call);
                                   

 Dbms_Lob.Createtemporary(Lob_Loc => vblob,
                                   Cache   => TRUE,
                                   Dur     => Dbms_Lob.Call);                                   

  SELECT agreement_doc, mimetype  INTO vClob, vmimetype
                FROM suppliers
                WHERE supplier_id = :P2_SUPPLIER_ID;

-- tranform the input CLOB into a BLOB of the desired charset
begin
    DBMS_LOB.CONVERTTOBLOB( DEST_LOB     => vblob,
                            SRC_CLOB     => vclob,
                            AMOUNT       => DBMS_LOB.LOBMAXSIZE,
                            DEST_OFFSET  => L_DEST_OFFSET,
                            SRC_OFFSET   => L_SRC_OFFSET,
                            BLOB_CSID    => NLS_CHARSET_ID('WE8MSWIN1252'),
                            LANG_CONTEXT => L_LANG_CONTEXT,
                            WARNING      => L_WARNING
                          );
end;                          
                
  owa_util.mime_header(vmimetype,false);
  htp.p('Content-Length: ' || dbms_lob.getlength(vblob)); 
  owa_util.http_header_close;  
  wpg_docload.download_file(vblob);
  exception 
  when no_data_found then
   null;
 when others then 
   null;
  
END;

Below is the screenshot for the above setting:

After that click on the Next button and on the next step click on the Create Process button.

Now come back to your page where you created the report and follow the remaining steps:

6. Create a JavaScript Function

Click on the page and in the Properties, palette add the following JavaScript code in the Function and Global Variable Declaration section:

function getClob(p_supplier_id)
{ 
    
    apex.item( "P2_SUPPLIER_ID" ).setValue (p_supplier_id);
    
    document.getElementById("myFrame1").src = "f?p=&APP_ID.:0:&SESSION.:APPLICATION_PROCESS=preview_clob_data:NO:RP:P2_SUPPLIER_ID:" + p_supplier_id;

    apex.jQuery('#preview1').trigger('apexrefresh');

}

7. Add JavaScript Code to Make the Preview Region Sticky

The Preview region, we created in the 4th step, should be sticky when the user will scroll the report. So add the following JavaScript code in the Execute when Page Loads section as shown below:

$("#preview1").stickyWidget({toggleWidth:true});

Below is the screenshot for the above JavaScript code reference:

8. Create a Link for Preview in the Interactive Report

Click on the Preview column of the report and set the type as Link and paste the following JavaScript code for the Link Target as URL type: (Also shown in the below image)

javascript:getClob(#SUPPLIER_ID#);

Save the changes and run the page to test. Now when you will click on the Preview link it will display the CLOB contents in the Static Region without refreshing the whole page.

Do you think it is complicated? Don't worry you can download this Oracle Apex application from the GitHub with the link below:

Download this project from GitHub

23 thoughts on “Displaying CLOB Contents in Oracle Apex”

Marc
August 19, 2020 at 10:35 am
Hello,
I have tried a little modified code but unfortunately I always get Oracle get data services
400 Bad Request{timeStamp} | {requestId}
Reply
- Vinish Kapoor
  August 19, 2020 at 10:44 am
  I think you are missing something because the above code is tested.
  I have given the link above to download this app from GitHub, you should download it and install it in your workspace to test.
  Then you can import that specific page from this app to your application.
- Marc
  August 20, 2020 at 6:09 am
  Thanks for fast response.
  I have installed the app and it worked well until I set longer supplier_id := 12345678901234567890. In that case strange behaviour started. Somethimes I have got error (400 Bad Request{timeStamp} | {requestId}), sometimes nothing, sometimes worked well.....
- Vinish Kapoor
  August 20, 2020 at 6:15 am
  Is this supplier id really exists? if not then you should not have to worry about it.
  You can do one more thing, in the Ajax process, modify the Exception area as below:
```
Exception
   when no_data_found then
     htp.p('Supplier id not found.');
   when others then
     htp.p('An error occurred.');
End;
```
  After making the above changes, it will not show any other error messages. Please try.
- Marc
  August 20, 2020 at 6:33 am
  Hello,
  in case supplier_id = 1 - OK
  in case supplier_id = 123456789012345678 'Supplier id not found.'
- Vinish Kapoor
  August 20, 2020 at 6:36 am
  Then it means it is not found. You should check in your database.
- Marc
  August 20, 2020 at 7:41 am
  I won't bother anymore.
  I doubt it is Database (Suppliers), It is only one row with supplier_id edited and tested with different values (lengths) using SQL Workshop, Tables, Data Edit. It seems that a length of the supplier_id is the reason because the problem occurs only if lenght > certain lenght.
  If I replace in prew_clob_data in select, WHERE, P2_SUPPLIER_ID with value '12345678901234567890' (suppliers_id in the table) works well, so I suppose that the problem is 'transfer' P2_SUPPLIER_ID to prew_clob_data if the length is too long.
  Anyway, best regards
- Marc
  August 20, 2020 at 6:22 am
  Another one result in Preview window after Preview button clicked:
  xjnr4bcss0cbo6c-dbparbih.adb.eu-frankfurt-1.oraclecloudapps.com refused to connect.
- Vinish Kapoor
  August 20, 2020 at 6:29 am
  It seems like connection issue. I have no idea about it. I have just tested this app here and it is working fine.
- Tor
  October 31, 2020 at 2:02 am
  Did you turn off friendly URLs? I had the same problem with friendly URLs turned on
Mike
September 23, 2020 at 6:09 am
Hi Vinish,
Is this possible with a blob instead of a clob?
I need the user to be able to preview a pdf using your method here, or the user will download the pdf.
Please let me know, thank you.
Reply
- Vinish Kapoor
  September 23, 2020 at 6:12 am
  Yes, please check the following link:
  Display BLOB contents (images/PDF) on page in Oracle Apex
- Mike
  September 23, 2020 at 7:30 am
  Awesome, thank you.
Tor
October 31, 2020 at 2:01 am
This is great, thank you for this! But it only seems to work if friendly URLs is turned off in Application Definition Attributes I assume because of this which use the old non friendly URL
```
document.getElementById("myFrame1").src = "f?p=&APP_ID.:0:&SESSION.:APPLICATION_PROCESS=preview_clob_data:NO:RP:P2_SUPPLIER_ID:" + p_supplier_id;
```
I tried to change it to:
document.getElementById("myFrame1").src = apex.util.makeApplicationUrl({pageId:0,session: $v( "pInstance" ), request: 'APPLICATION_PROCESS=preview_clob_data',itemNames:['P2_SUPPLIER_ID'], itemValues:[p_supplier_id]});
But that also only work with Friendly URLs turned off. Do you have a solution for friendly URLs?
Reply
- Vinish Kapoor
  October 31, 2020 at 8:04 am
  If using friendly URL then me also facing some issues in passing parameter. But so far I found the following approach:
  Change the static region content as follows:
```
<p align="center">
<iframe id="myFrame1" src="f?p=&APP_ID.:0:&SESSION.:APPLICATION_PROCESS=preview_clob_data" width="99%" height="750">
</iframe>
</p>
```
  Change the getClob function as follows:
```
function getClob(p_supplier_id)
{ 
    
    apex.item( "P2_SUPPLIER_ID" ).setValue (p_supplier_id);
    apex.submit('P2_SUPPLIER_ID'); 
    document.getElementById("myFrame1").src = "f?p=&APP_ID.:0:&SESSION.:APPLICATION_PROCESS=preview_clob_data";

}
```
  In this case, I am not passing the supplier id as parameter, instead setting the item value and submitting it using the apex.submit() method.
- Tor Loege
  November 1, 2020 at 12:56 am
  Thanks Vinish! Works like a charm!
- Tor Loege
  November 1, 2020 at 2:36 am
  Thanks but I just realized that with this method, the page is submitted every time you click on preview. That obviously takes longer but more importantly it means you lose your place in the report.
  Oh well, no big deal I will just use the old URL "unfriendly" URL construct for this app.
- Vinish Kapoor
  November 1, 2020 at 7:47 am
  Yes, that is the problem. I am looking for the solution to how to pass the parameters to application process URL in friendly URL format. Yesterday I tried everything but it didn't work.
  When I will resolve this I will comment again here to let you know.
- Vinish Kapoor
  November 1, 2020 at 11:05 am
  Finally, the following approach is working with friendly URL without submitting the whole page.
  Revert the static region changes:
```
<p align="center">
<iframe id="myFrame1" src="" width="99%" height="750">
</iframe>
</p>
```
```
function getClob(p_supplier_id)
{ 
    
    apex.item( "P2_SUPPLIER_ID" ).setValue (p_supplier_id);

 // below code will set the p2_supplier_id value
  apex.server.process ( "SAVE_HIDDEN_VALUE_IN_SESSION_STATE", {
     x01: "set_session_state",
     pageItems: "#P2_SUPPLIER_ID"
     }, {dataType: 'text'} );

    document.getElementById("myFrame1").src = "f?p=&APP_ID.:0:&SESSION.:APPLICATION_PROCESS=preview_clob_data";

}
```
  The above JavaScript code will set the page item value p2_supplier_id including its session state so that the Ajax process can see it.
- Tor Loege
  November 1, 2020 at 9:28 pm
  Very good looks great! Thank you sir!
Ivan
December 17, 2020 at 7:37 pm
Hi
I have a question: how can I make a modal window or a form from the region "Preview" so that it opens when the link is clicked.
That is, I want to display the preview only when clicked and in front of the main region and close it after viewing.
Reply
Venkat
May 21, 2021 at 3:09 am
I have a slightly different use case where I am generating html content on the fly using PL/SQL code. For some reason, the provided JS code to set the iframe source didn't work. Searched the internet and found it. But this works now: document.getElementById("myFrame1").src = "javascript:'"+html_content+"'";
Reply
Maarten
November 3, 2021 at 2:45 pm
This is a clever approach, thanks for sharing.
But I'm having an issue, the files keeps getting downloaded in stead of it's contents showing in the preview region.
Reply