wu-sheng commented on pull request #8684:
URL: https://github.com/apache/skywalking/pull/8684#issuecomment-1067981124
For making reviewers easier, here are the key points.
## New StorageBuilder
```java
/**
* Converter between the give T and K.
*
* @param <T> A storage entity implementation.
*/
public interface StorageBuilder<T extends StorageData> {
/**
* Use the given converter to build an OAP entity object.
*
* @param converter to transfer data format
* @return an OAP entity object
*/
T storage2Entity(Convert2Entity converter);
/**
* Use the given converter to build a database preferred structure.
*
* @param entity to be used
* @param converter provides the converting logic and hosts the
converted value. Use {@link
* Convert2Storage#obtain()} to read the converted data.
*/
void entity2Storage(T entity, Convert2Storage converter);
}
```
StorageBuilder wouldn't accept HashMap as a parameter or the return value,
now `Convert2Entity` and `Convert2Storage` interfaces open the responsibility
of this temporary value holder to the storage plugin implementations.
## Default HashMapConverter
To keep all codes are changed smoothly, I introduced `HashMapConverter` as
the default converter. @lujiajing1126 Such as BanyanDB plugin could use its
native one, and use native structure and get rid of HashMap permanently.
```java
public class HashMapConverter {
/**
* Stateful Hashmap based converter, build object from a HashMap type
source.
*/
@RequiredArgsConstructor
public static class ToEntity implements Convert2Entity {
private final Map<String, Object> source;
@Override
public Object get(final String fieldName) {
return source.get(fieldName);
}
}
/**
* Stateful Hashmap based converter, from object to HashMap.
*/
public static class ToStorage implements Convert2Storage<Map<String,
Object>> {
private Map<String, Object> source;
public ToStorage() {
source = new HashMap();
}
@Override
public void accept(final String fieldName, final Object fieldValue) {
source.put(fieldName, fieldValue);
}
@Override
public Object get(final String fieldName) {
return source.get(fieldName);
}
@Override
public Map<String, Object> obtain() {
return source;
}
}
}
```
This **HashMapConverter** is super easy, just as a wrapper of HashMap.
____
All other code changes are just following these two proposals, and making
codes work as usual.
Notice, there could be more potential changes for JDBC and other storage
plugins, such as wrap ResultSet as a new ToEntity, rather than
`ResultSet->HashMap->Entity`
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