Elastcsearch官方提供了一個elasticsearch-rest-high-level-client，作者在寫bug的時候需要將其中的ActionRequest（子類包括SearchRequest、IndexRequest、UpdateRequest等）和SearchResponse類分別做序列化和反序列化。

首先，這兩個類都沒有實現Serializable介面也無法直接用Json工具序列化為Json字串。但是官方給我們提供了其它方法，親測有效，以下作為記錄：

ActionRequest(使用SearchRequest作例子)：

官方提供了readFrom(StreamInput in)和writeTo(StreamOutput out)方法供使用

public abstract class ActionRequest extends TransportRequest {

  ...

    @Override
    public void readFrom(StreamInput in) throws IOException {
        super.readFrom(in);
    }

    @Override
    public void writeTo(StreamOutput out) throws IOException {
        super.writeTo(out);
    }
...
}
 

所以，我們實現序列化的核心程式碼如下：

        BytesStreamOutput output = new BytesStreamOutput();
        actionRequest.writeTo(output);
        //用base64進行編碼（如果沒有這步，反序列化時會失敗）
        String s = BaseCoder.encryptBASE64(output.bytes().toBytesRef().bytes);

反序列化：

         //base64解碼
        byte[] s1 = BaseCoder.decryptBASE64(s);
        BytesStreamOutput bytesStreamOutput = new BytesStreamOutput();
        bytesStreamOutput.write(s1);

        //設定解析器
        IndicesModule indicesModule = new IndicesModule(Collections.emptyList());
        SearchModule searchModule = new SearchModule(Settings.EMPTY, false, Collections.emptyList());
        List<NamedWriteableRegistry.Entry> entries = new ArrayList<>();
        entries.addAll(indicesModule.getNamedWriteables());
        entries.addAll(searchModule.getNamedWriteables());
        NamedWriteableRegistry namedWriteableRegistry = new NamedWriteableRegistry(entries);
        //轉換成輸入流
        StreamInput in= new
NamedWriteableAwareStreamInput(bytesStreamOutput.bytes().streamInput(), namedWriteableRegistry);
        
        //還原
        SearchRequest request = new SearchRequest();
        actionRequest.readFrom(in);
       
 

SearchResponse:

作者在對SearchResponse僅需序列化處理時發現上面的辦法行不通，於是換了一個辦法。es給我們提供了json的解決方式（XContent）。

序列化：

 XContentBuilder builder = XContentFactory.jsonBuilder();
        XContentBuilder xContent = searchResponse.toXContent(builder, ToXContent.EMPTY_PARAMS);
        String jsonResponse = xContent.string();

反序列化：

 NamedXContentRegistry namedXContentRegistry = new NamedXContentRegistry(getDefaultNamedXContents());
        XContentParser parser = JsonXContent.jsonXContent.createParser(namedXContentRegistry, jsonResponse);

 SearchResponse response= SearchResponse.fromXContent(parser)；

private static List<NamedXContentRegistry.Entry> getDefaultNamedXContents() {
        Map<String, ContextParser<Object, ? extends Aggregation>> map = new HashMap<>();
        //這裡設定統計欄位（Aggregation)
        map.put(TopHitsAggregationBuilder.NAME, (p, c) -> ParsedTopHits.fromXContent(p, (String) c));
        map.put(DateRangeAggregationBuilder.NAME, (p, c) -> ParsedDateRange.fromXContent(p, (String) c));
        map.put(FilterAggregationBuilder.NAME, (p, c) -> ParsedFilter.fromXContent(p, (String) c));
        map.put(StringTerms.NAME, (p, c) -> ParsedStringTerms.fromXContent(p, (String) c));
        map.put(LongTerms.NAME, (p, c) -> ParsedLongTerms.fromXContent(p, (String) c));
        map.put(DoubleTerms.NAME, (p, c) -> ParsedDoubleTerms.fromXContent(p, (String) c));
        List<NamedXContentRegistry.Entry> entries = map.entrySet().stream()
                .map(entry -> new NamedXContentRegistry.Entry(Aggregation.class, new ParseField(entry.getKey()), entry.getValue()))
                .collect(Collectors.toList());
        SearchModule searchModule = new SearchModule(Settings.EMPTY, false, Collections.EMPTY_LIST);
        //普通欄位
        entries.addAll(searchModule.getNamedXContents());
        return entries;
    }