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Batch Engine API Basics - Exporting Data

Liferay’s Headless Batch Engine provides REST APIs to import and export data. Call these services to export data from Liferay.

Exporting Data

Start a new Liferay DXP instance by running

docker run -it -m 8g -p 8080:8080 liferay/dxp:2024.q2.11

Sign in to Liferay at http://localhost:8080 using the email address test@liferay.com and the password test. When prompted, change the password to learn.

Then, follow these steps:

Download and unzip Batch Engine API Basics.

curl https://resources.learn.liferay.com/dxp/latest/en/headless-delivery/consuming-apis/liferay-g4j2.zip -O

unzip liferay-g4j2.zip

To export data, you must have the fully qualified class name of the entity you are exporting. You can get the class name from the API explorer in your installation at /o/api. Scroll down to the Schemas section and note down the x-class-name field of the entity you want to export.
Use the following cURL script to export accounts from your Liferay instance. On the command line, navigate to the curl folder. Execute the ExportTask_POST_ToInstance.sh script with the fully qualified class name of Account and json as parameters. The json parameter denotes the format of the exported data. It also supports jsont, jsonl and csv formats.
```
./ExportTask_POST_ToInstance.sh com.liferay.headless.admin.user.dto.v1_0.Account json
```
The JSON response shows the creation of a new export task. Note the id of the task:
```
{
   "className" : "com.liferay.headless.admin.user.dto.v1_0.Account",
   "contentType" : "JSON",
   "errorMessage" : "",
   "executeStatus" : "INITIAL",
   "externalReferenceCode" : "6c5286a2-aa28-175b-041e-eacca4a54d3b",
   "id" : 1234,
   "processedItemsCount" : 0,
   "totalItemsCount" : 0
}
```
Important

jsont is the required format for *.batch-engine-dat.json files when using in conjunction with batch client extensions.

When using json or jsonl as the output format, all fields are exported by default. To specify fields, you must provide an additional query parameter (fieldNames) with the fields you want to export. Each field must be separated by a comma (,). When using csv as the export format, this is a mandatory query parameter.
The current executeStatus is INITIAL. It denotes the submission of a task to the Batch Engine. You must wait until this is COMPLETED to download the data. On the command line, execute the ExportTask_GET_ById.sh script and replace 1234 with the ID of your export task.
```
./ExportTask_GET_ById.sh 1234
```
```
{
   "className" : "com.liferay.headless.admin.user.dto.v1_0.Account",
   "contentType" : "JSON",
   "endTime" : "2022-10-19T14:13:58Z",
   "errorMessage" : "",
   "executeStatus" : "COMPLETED",
   "externalReferenceCode" : "6c5286a2-aa28-175b-041e-eacca4a54d3b",
   "id" : 1234,
   "processedItemsCount" : 8,
   "startTime" : "2022-10-19T14:13:58Z",
   "totalItemsCount" : 8
}
```
If the executeStatus is COMPLETED, you can download the exported data. If not, execute the command again to ensure the task has finished execution. If the executeStatus shows FAILED, check the errorMessage field to understand what went wrong.
Once the executeStatus is COMPLETED, you can download the exported data by executing the ExportTaskContent_GET_ById.sh script and replacing 1234 with the ID of your export task.
```
./ExportTaskContent_GET_ById.sh 1234
```
This downloads the exported data as a .zip file in the current directory. Extract it and use an appropriate application to view the data.
You can also call the The REST service using the Java client. Navigate out of the curl folder and into the java folder. Compile the source files:
```
javac -classpath .:* *.java
```
Run the ExportTask_POST_ToInstance class. Replace able with the fully qualified name of the class.
```
java -classpath .:* -DclassName=able ExportTask_POST_ToInstance
```
For example, export Account data:
```
java -classpath .:* -DclassName=com.liferay.headless.admin.user.dto.v1_0.Account ExportTask_POST_ToInstance
```
Note the id of the export task from the JSON response.
Run the ExportTask_GET_ById class with the following command. Replace 1234 with the ID of your export task.
```
java -classpath .:* -DexportTaskId=1234 ExportTask_GET_ById
```
Once the executeStatus shows COMPLETED, you can download the data by running the ExportTaskContent_GET_ById class. Replace 1234 with the ID of your export task.
```
java -classpath .:* -DexportTaskId=1234 ExportTaskContent_GET_ById
```

Arguments	Description
`-H "Content-Type: application/json"`	Indicates that the request body format is JSON.
`-X POST`	The HTTP method to invoke at the specified endpoint
`"http://localhost:8080/o/headless-batch-engine/v1.0/export-task/${1}/${2}"`	The REST service endpoint
`-u "test@liferay.com:learn"`	Basic authentication credentials

Basic authentication is used here for demonstration purposes. For production, you should authorize users via OAuth2. See Using OAuth2 to Authorize Users for a sample React application that uses Oauth2.

Examine the Java Class

The ExportTask_POST_ToInstance.java class exports data by calling the Batch Engine related service.

public static void main(String[] args) throws Exception {
	ExportTaskResource.Builder builder = ExportTaskResource.builder();

	ExportTaskResource exportTaskResource = builder.authentication(
		"test@liferay.com", "learn"
	).build();

	ExportTask exportTask = exportTaskResource.postExportTask(
		String.valueOf(System.getProperty("className")), "json", null, null,
		null, "");

	System.out.println(exportTask);
}

This class invokes the REST service using only three lines of code:

Line (abbreviated)	Description
`ExportTaskResource.Builder builder = ...`	Gets a `Builder` for generating a `ExportTaskResource` service instance.
`ExportTaskResource exportTaskResource = builder.authentication(...).build();`	Specifies basic authentication and generates a `ExportTaskResource` service instance.
`exportTaskResource.postExportTask(...);`	Calls the `exportTaskResource.postExportTask` method and passes the data to post.

Note that the project includes the com.liferay.headless.batch.engine.client.jar file as a dependency. You can find client JAR dependency information for all REST applications in the API explorer in your installation at /o/api.

Note

The main method’s comment demonstrates running the class.

The other example Java classes are similar to this one, but call different ExportTaskResource methods.

Important

See ExportTaskResource for service details.

Below are examples of calling other Batch Engine export REST services using cURL and Java.

Get the ExportTask Status

You can get the status of an export task by executing the following cURL or Java command. Replace 1234 with the ID of your export task.

ExportTask_GET_ById.sh

Command:

./ExportTask_GET_ById.sh 1234

Code:

curl \
	"http://localhost:8080/o/headless-batch-engine/v1.0/export-task/${1}" \
	--user "test@liferay.com:learn"

ExportTask_GET_ById.java

Run the ExportTask_GET_ById class. Replace 1234 with the ID of your export task.

Command:

java -classpath .:* -DexportTaskId=1234 ExportTask_GET_ById

Code:

public static void main(String[] args) throws Exception {
	ExportTaskResource.Builder builder = ExportTaskResource.builder();

	ExportTaskResource exportTaskResource = builder.authentication(
		"test@liferay.com", "learn"
	).build();

	System.out.println(
		exportTaskResource.getExportTask(
			Long.valueOf(System.getProperty("exportTaskId"))));
}

Exporting Data from a Site

You can export data from a site by executing the following cURL or Java command. The example below exports blog posts from a site. Find your Site’s ID and replace 1234 with it. When using another entity, you must also update the fully qualified class name parameter in the cURL script.

ExportTask_POST_ToSite.sh

Command:

./ExportTask_POST_ToSite.sh com.liferay.headless.delivery.dto.v1_0.BlogPosting json 1234

Code:

curl \
	"http://localhost:8080/o/headless-batch-engine/v1.0/export-task/${1}/${2}?siteId=${3}" \
	--header "Content-Type: application/json" \
	--request "POST" \
	--user "test@liferay.com:learn"

ExportTask_POST_ToSite.java

Run the ExportTask_POST_ToSite class. Replace 1234 with your site’s ID and able with the fully qualified name of the class you want to export:

java -classpath .:* -DsiteId=1234 -DclassName=able ExportTask_POST_ToSite

For example, export BlogPosting data:

java -classpath .:* -DsiteId=1234 -DclassName=com.liferay.headless.delivery.dto.v1_0.BlogPosting ExportTask_POST_ToSite

Code:

public static void main(String[] args) throws Exception {
	ExportTaskResource.Builder builder = ExportTaskResource.builder();

	ExportTaskResource exportTaskResource = builder.authentication(
		"test@liferay.com", "learn"
	).parameter(
		"siteId", String.valueOf(System.getProperty("siteId"))
	).build();

	ExportTask exportTask = exportTaskResource.postExportTask(
		String.valueOf(System.getProperty("className")), "json", null, null,
		null, "");

	System.out.println(exportTask);
}

Note

The second parameter is json and denotes the output format of the exported data. You can also use jsonl and csv here. If using CSV, it is mandatory to specify the fields you want to export as a comma separated string and pass it as the fifth parameter in the exportTaskResource.postExportTask() method.

The JSON response displays information of the newly created export task. Note the id to keep track of its executeStatus. Once completed, you can execute ExportTaskContent_GET_ById.[java|sh] with the export task ID to download the data.

Exporting Custom Objects

To export custom objects, you must provide the ObjectEntry class’s class name in the URL and pass the object’s name in the taskItemDelegateName query parameter. For example, this command exports instance-scoped Able’s entries:


curl  \
    "http://localhost:8080/o/headless-batch-engine/v1.0/export-task/com.liferay.object.rest.dto.v1_0.ObjectEntry/json?taskItemDelegateName=C_Able" \
    --header "Content-Type: application/json" \
    --request "POST" \
    --user "test@liferay.com:learn"

Get Contents of the Exported Data

You can download the exported data with the following cURL and Java commands. Replace 1234 with the export task’s ID. It is then downloaded as a .zip file in the current directory.

ExportTaskContent_GET_ById.sh

Command:

./ExportTaskContent_GET_ById.sh 1234

Code:

curl \
	"http://localhost:8080/o/headless-batch-engine/v1.0/export-task/${1}/content" \
	--output file.zip \
	--user "test@liferay.com:learn"

ExportTaskContent_GET_ById.java

Command

java -classpath .:* -DexportTaskId=1234 ExportTaskContent_GET_ById

Code:

public static void main(String[] args) throws Exception {
	ExportTaskResource.Builder builder = ExportTaskResource.builder();

	ExportTaskResource exportTaskResource = builder.authentication(
		"test@liferay.com", "learn"
	).build();

	HttpInvoker.HttpResponse httpResponse =
		exportTaskResource.getExportTaskContentHttpResponse(
			Long.valueOf(System.getProperty("exportTaskId")));

	try (FileOutputStream fileOutputStream = new FileOutputStream(
			"file.zip")) {

		fileOutputStream.write(httpResponse.getBinaryContent());
	}
}

The API Explorer lists all of the Headless Batch Engine services and schemas and has an interface to try out each service.

Capability: