solr dataimport 数据导入源码分析（四）

vivion27

　　我们查看DocBuilder类的源码发现，并不是直接持有对SqlEntityProcessor类的引用，而是另外一个包装类EntityProcessorWrapper，EntityProcessorWrapper直接继承自抽象类EntityProcessor，而不是继承自中间的EntityProcessorBase类，简要类图如下
包装类额外添加了缓存处理以及格式转换等功能，然后调用SqlEntityProcessor相应方法进行处理，相当于SqlEntityProcessor的代理类，共同继承自抽象类EntityProcessor（SqlEntityProcessor 是通过EntityProcessorBase 间接继承自EntityProcessor）
　　EntityProcessorWrapper类的简要代码如下

public class EntityProcessorWrapper extends EntityProcessor {
  private static final Logger log = LoggerFactory.getLogger(EntityProcessorWrapper.class);

  EntityProcessor delegate;
  private DocBuilder docBuilder;

  String onError;
  Context context;
  protected VariableResolverImpl resolver;
  String entityName;

  protected List transformers;

  protected List rowcache;

  public EntityProcessorWrapper(EntityProcessor delegate, DocBuilder docBuilder) {
    this.delegate = delegate;
    this.docBuilder = docBuilder;
  }

  @Override
  public void init(Context context) {

    delegate.init(context);

  }
  
  protected Map getFromRowCache() {
    if (rowcache.isEmpty()){
      return null;
    }
    return rowcache.remove(0);
  }

  @Override
  public Map nextRow() {
    pullRow();
  }
  

  protected Map pullRow() {
    Map arow = null;
    try {
      arow = delegate.nextRow();
    } catch (Exception e) {
      if (ABORT.equals(onError)) {
        wrapAndThrow(SEVERE, e);
      } else {
        // SKIP is not really possible. If this calls the nextRow() again the
        // Entityprocessor would be in an inconistent state
        log.error("Exception in entity : " + entityName, e);
        return null;
      }
    }
    log.debug("arow : {}", arow);
    return arow;
  }

  @Override
  public Map nextModifiedRowKey() {
    Map row = delegate.nextModifiedRowKey();
    row = applyTransformer(row);
    rowcache = null;
    return row;
  }

  @Override
  public Map nextDeletedRowKey() {
    Map row = delegate.nextDeletedRowKey();
    row = applyTransformer(row);
    rowcache = null;
    return row;
  }

  @Override
  public Map nextModifiedParentRowKey() {
    return delegate.nextModifiedParentRowKey();
  }

  @Override
  public void destroy() {
    delegate.destroy();
  }
  

  @Override
  public void close() {
    delegate.close();
  }　　}