Using JDK8 Stream how to iterate the nested objects

user_6715184 0
Viewed 96

I am using JDK8 streams in my project .

From the third party application i am going to get the soap xml response mentioned below . According to requirement i have to capture the MetaDataItem which contains the ExecutionCode and the corresponding Value .

<Response>
    <ProcessingResults>
      <Identifier>identifier-A</Identifier>
      <StepResult>
        <Identifier>device</Identifier>
        <DataItem>
          <Identifier>key</Identifier>
          <MetaData>
            <MetaDataItem>
              <Name>ExecutionCode</Name>
              <Value>0</Value>
            </MetaDataItem>
          </MetaData>
        </DataItem>
      </StepResult>
    </ProcessingResults>
  </Response>

I am not sure how can i traverse the object till MetaDataItem using JDK8 Streams. I tried but no luck for me

In my JAXB classes 

 1. Response class contains "List<ProcessingResults>". 
 2. Each ProcessingResult class contains the "List<StepResults>".
 3. StepResult class contains the "List<DataIteam>".
 4. DataItem class contains the "List<MetaDataItem>".
java-stream java-8 mapping collections java
2 Answers

All you have to do is apply sequence of flatMap operators to get what you need. Here's how it looks,

List<MetaDataItem> metaDataItms = response.getProcessingResult().stream()
        .flatMap(pr -> pr.getStepResults().stream())
        .flatMap(sr -> sr.getDataItms().stream())
        .flatMap(ditm -> ditm.getMetaDataItems().stream())
        .collect(Collectors.toList());
user_41085900

Looks like you need Stream.flatMap. Try this:

List<MetaDataItem> list= 
    response.getProcessingResult().stream()
            .map(ProcessingResult::getStepResults).flatMap(Collection::stream) 
            .map(StepResult::getDataItms).flatMap(Collection::stream) 
            .map(DataItem::getMetaDataItems).flatMap(Collection::stream) 
            .collect(Collectors.toList());
user_105846050
Related