Java 遍历急切地收集节点的所有关系，如下所示： public class SpecificRelsPathExpander implements PathExpander, Predicate<Relationship> { private final String requiredProperty; public SpecificRelsPathExpander( String requiredProperty ) { this.requiredProperty = requiredProperty; } @Override public Iterable<Relationship> expand( Path path, BranchState state ) { Iterable<Relationship> rels = path.endNode().getRelationships( RelTypes.FOO, Direction.BOTH ); return Iterables.filter( this, rels ); } @Override public boolean accept( Relationship relationship ) { return requiredProperty.equals( relationship.getProperty( "propertyName", null ) ); } // not used @Override public PathExpander<Object> reverse() { return null; } } public类specificRelsPathPander实现PathExpander，谓词 { 私有最终字符串requiredProperty； 公共SpecificRelsPathExpander（字符串requiredProperty） { this.requiredProperty=requiredProperty； } @凌驾 公共Iterable扩展（路径、分支状态） { Iterable rels=path.endNode（）.getRelationships（RelTypes.FOO，Direction.BOTH）； 返回Iterables.filter（this，rels）； } @凌驾 公共布尔接受（关系） { 返回requiredProperty.equals（relationship.getProperty（“propertyName”，null））； } //不用 @凌驾 公共路径扩展器反向（） { 返回null； } }

此外，只要客户端（即从开始遍历调用时接收到的迭代器所在的客户端）拥有next/next，遍历就会继续。将不会单独进行遍历，这一切都发生在hasNext/next中。

这是一个很好的改进，肯定有助于实现目标。但问题仍然存在，有可能扩展一个具有数百个关系的节点，这将导致（有几个类似的节点）遍历中排队的路径快速增长。我需要一个更严格的约束，可以立即停止遍历。这是一个很好的改进，肯定有助于实现目标。但问题仍然存在，有可能扩展一个具有数百个关系的节点，这将导致（有几个类似的节点）遍历中排队的路径快速增长。我需要一个更严格的约束，可以立即停止遍历。这是一个很好的改进，肯定有助于实现目标。但问题仍然存在，有可能扩展一个具有数百个关系的节点，这将导致（有几个类似的节点）遍历中排队的路径快速增长。我需要一个更严格的约束，可以立即停止遍历。

private class IncludePathWithTargetPropertyEvaluator implements Evaluator {

private String targetProperty;
private int results;
private long startTime, curTime, elapsed;       

public IncludePathWithTargetPropertyEvaluator(String targetProperty) {
    this.targetProperty = targetProperty;
    this.startTime = System.currentTimeMillis();
    this.results = 0;
}

public Evaluation evaluate(Path path) {

    curTime = System.currentTimeMillis();
    elapsed = curTime - startTime;

    if (elapsed >= 200) {
        return Evaluation.EXCLUDE_AND_PRUNE;
    }

    if (results >= 3) {
        return Evaluation.EXCLUDE_AND_PRUNE;
    }

    String property = (String) path.endNode().getProperty("propertyName");

    if (property.equals(targetProperty)) {
        results = results + 1;
        return Evaluation.INCLUDE_AND_PRUNE;
    }

    return Evaluation.EXCLUDE_AND_CONTINUE;
}

private class SpecificRelsPathExpander implements PathExpander {

private String requiredProperty;

public SpecificRelsPathExpander(String requiredProperty) {
    this.requiredProperty = requiredProperty;
}

public Iterable<Relationship> expand(Path path, BranchState<Object> state) {
    Iterable<Relationship> rels = path.endNode().getRelationships(RelTypes.FOO, Direction.BOTH);
    if (!rels.iterator().hasNext())
        return null;
    List<Relationship> validRels = new LinkedList<Relationship>();
    for (Relationship rel : rels) {
        String property = (String) rel.getProperty("propertyName");
        if (property.equals(requiredProperty)) {
            validRels.add(rel);
        }
    }
    return validRels;
}

// not used
public PathExpander<Object> reverse() {
    return null;
}

private class SpecificRelsPathExpander implements PathExpander {

private String requiredProperty;
private long startTime, curTime, elapsed;

public SpecificRelsPathExpander(String requiredProperty) {
    this.requiredProperty = requiredProperty;
    this.startTime = System.currentTimeMillis();
}

public Iterable<Relationship> expand(Path path, BranchState<Object> state) {
    curTime = System.currentTimeMillis();
    elapsed = curTime - startTime;

    if (elapsed >= 200) {
        return null;
    }

    Iterable<Relationship> rels = path.endNode().getRelationships(RelTypes.FOO, Direction.BOTH);
    if (!rels.iterator().hasNext())
        return null;
    List<Relationship> validRels = new LinkedList<Relationship>();
    for (Relationship rel : rels) {
        String property = (String) rel.getProperty("propertyName");
        if (property.equals(requiredProperty)) {
            validRels.add(rel);
        }
    }
    return validRels;
}

// not used
public PathExpander<Object> reverse() {
    return null;
}

public class SpecificRelsPathExpander implements PathExpander, Predicate<Relationship>
{
    private final String requiredProperty;

    public SpecificRelsPathExpander( String requiredProperty )
    {
        this.requiredProperty = requiredProperty;
    }

    @Override
    public Iterable<Relationship> expand( Path path, BranchState state )
    {
        Iterable<Relationship> rels = path.endNode().getRelationships( RelTypes.FOO, Direction.BOTH );
        return Iterables.filter( this, rels );
    }

    @Override
    public boolean accept( Relationship relationship )
    {
        return requiredProperty.equals( relationship.getProperty( "propertyName", null ) );
    }

    // not used
    @Override
    public PathExpander<Object> reverse()
    {
        return null;
    }
}