code: public RESTImport createImportJob(String workSpaceName, String dataStoreName)
          throws Exception {
  
          if (StringUtils.isEmpty(workSpaceName)) {
              throw new GeoServerRESTImporterException("No workspace given. Please provide a "
                  + "workspace to import the data in.");
          }
  
          RESTImport importJob = new RESTImport();
  
          LOG.debug("Creating a new import job to import into workspace " + workSpaceName);
  
          RESTTargetWorkspace targetWorkspace = new RESTTargetWorkspace(workSpaceName);
          importJob.setTargetWorkspace(targetWorkspace);
  
          if (!StringUtils.isEmpty(dataStoreName)) {
              LOG.debug("The data will be imported into datastore " + dataStoreName);
              RESTTargetDataStore targetDataStore = new RESTTargetDataStore(dataStoreName, null);
              importJob.setTargetStore(targetDataStore);
          } else {
              LOG.debug("No datastore given. A new datastore will be created in relation to the"
                  + "input data.");
          }
  
          Response httpResponse = HttpUtil.post(
              this.addEndPoint(""),
              this.asJSON(importJob),
              ContentType.APPLICATION_JSON,
              this.username,
              this.password
          );
  
          HttpStatus responseStatus = httpResponse.getStatusCode();
          if (responseStatus == null || !responseStatus.is2xxSuccessful()) {
              throw new GeoServerRESTImporterException("Import job cannot be "
                  + "created. Is the GeoServer Importer extension installed?");
          }
  
          RESTImport restImport = (RESTImport) this.asEntity(httpResponse.getBody(), RESTImport.class);
  
          LOG.debug("Successfully created the import job with ID " + restImport.getId());
  
          return restImport;
      }
docs: Create a new import job.