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# Storage & I/O Framework
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Pluggable storage abstraction for form data with support for JSON storage, import/export operations, and custom storage adapters.
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## Capabilities
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### Storage Adapter Interface
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```java { .api }
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interface DDMStorageAdapter {
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    long create(DDMStorageAdapterSaveRequest ddmStorageAdapterSaveRequest) throws StorageException;
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    void deleteByClass(long ddmStructureId) throws StorageException;
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    void deleteByClassPK(long ddmStructureId, String ddmStructureKey, long classPK) throws StorageException;
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    DDMStorageAdapterGetResponse get(DDMStorageAdapterGetRequest ddmStorageAdapterGetRequest) throws StorageException;
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    void update(DDMStorageAdapterSaveRequest ddmStorageAdapterSaveRequest) throws StorageException;
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}
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class DDMStorageAdapterSaveRequest {
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    long getClassPK();
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    DDMFormValues getDDMFormValues();
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    long getDDMStructureId();
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    ServiceContext getServiceContext();
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}
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class DDMStorageAdapterGetResponse {
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    DDMFormValues getDDMFormValues();
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}
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```
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### I/O Operations
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```java { .api }
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interface DDMFormInstanceRecordExporter {
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    byte[] export(long formInstanceId, int status) throws PortalException;
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}
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interface DDMFormValuesDeserializer {
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    DDMFormValues deserialize(String content);
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}
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interface DDMFormValuesSerializer {
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    String serialize(DDMFormValues ddmFormValues);
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}
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```
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## Usage Examples
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### Custom Storage Implementation
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```java
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@Component
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public class CustomStorageExample implements DDMStorageAdapter {
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    @Override
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    public long create(DDMStorageAdapterSaveRequest request) throws StorageException {
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        DDMFormValues formValues = request.getDDMFormValues();
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        // Implement custom storage logic
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        return storeFormData(formValues);
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    }
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    @Override
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    public DDMStorageAdapterGetResponse get(DDMStorageAdapterGetRequest request) throws StorageException {
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        long classPK = request.getClassPK();
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        DDMFormValues formValues = retrieveFormData(classPK);
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        DDMStorageAdapterGetResponse response = new DDMStorageAdapterGetResponse();
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        response.setDDMFormValues(formValues);
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        return response;
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    }
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    private long storeFormData(DDMFormValues formValues) {
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        // Custom storage implementation
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        return System.currentTimeMillis(); // Return generated ID
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    }
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    private DDMFormValues retrieveFormData(long classPK) {
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        // Custom retrieval implementation
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        return new DDMFormValues();
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    }
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}
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```