Class Visualizer

fe/src/test/java/org/apache/impala/util/treevis/Visualizer.java:49–252

Visualizes a tree structure. Walks the tree, printing most fields of most objects. Excludes fields from the Object class, objects that would cause a cycle, and those specifically requested to ignored. Prints scalar-like values directly, else expands objects and array-like objects (including collecti

 * the object's fields.
 */
public class Visualizer {

  /**
   * Performs actual visualization of the tree based on
   * a set of events.
   */
  public interface TreeVisualizer {
    void startObj(String name, Object obj);
    void startArray(String name);
    void field(String name, Object value);
    void elide(String name, Object value, String reason);
    void emptyArray(String name);
    void endArray();
    void endObj();
  }

  private static final Class<?> STD_SCALARS[] = {
      Byte.class,
      Integer.class,
      Character.class,
      Long.class,
      Float.class,
      Double.class,
      String.class,
      Boolean.class,
      Enum.class,
      AtomicLong.class,
      BigDecimal.class,
      BigInteger.class
  };

  private TreeVisualizer treeVis_;
  private Set<Class<?>> scalarTypes_ = new HashSet<>();
  private Set<Class<?>> ignoreTypes_ = new HashSet<>();
  // Infinite recursion preventer.
  // Since there is no IdentityHashMap. Values ignored.
  private Map<Object, Object> parents_ = new IdentityHashMap<>();
  private int depthLimit_ = Integer.MAX_VALUE;

  public Visualizer(TreeVisualizer treeVis) {
    this.treeVis_ = treeVis;
    for (Class<?> c : STD_SCALARS) {
      scalarTypes_.add(c);
    }
  }

  /**
   * Specify a class to ignore. Objects of this type are
   * skipped during visualization, with a special message
   * for that field in place of object expansion.
   *
   * @param cls the class to skip
   */
  public void ignore(Class<?> cls) {
    ignoreTypes_.add(cls);
  }

  /**