elasticsearch2.4升级至5.2.2版本，SearcherSourceBuilder的json字符串转成SearcherSourceBuilder对象

最近在做一个项目的ES版本升级，从2.4升级至5.2版。由于升级版本跨度比较大，一些Java api都已经废弃了。原来的api，SearchRequestBuilder支持setSource()参数为json格式的字符串。

（1）ES2.4 SearchRequestBuilder setSource方法

public SearchRequestBuilder setSource(String source) {
        request.source(source);
        return this;
}

（2）ES5.2 SearchRequestBuilder setSource方法

public SearchRequestBuilder setSource(SearchSourceBuilder source) {
        request.source(source);
        return this;
}

因此，将String json类型转换为SearchSourceBuilder类型，方法如下。

String str = "ES2.4的json";
Settings settings = Settings.builder().build();
SearchModule searchModule = new SearchModule(settings, true, new ArrayList<>());
NamedXContentRegistry xContentRegistry = new NamedXContentRegistry(Stream.of(            searchModule.getNamedXContents().stream()).flatMap(Function.identity()).collect(toList()));

XContentType xContentType = XContentType.JSON();
XContentParser xContentParser = xContentType.xContent().createParser(NamedXContentRegistry.EMPTY,str);
QueryParseContext queryParseContext = new QueryParseContext(xContentParser);
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.parseXContent(queryParseContext);

具体也可参看：https://elasticsearch.cn/question/4553