如何使用片段检查Java中请求的GraphQL字段

Question

我有一个类似于以下的GraphQL查询：

query {
getPosts {    
...PostFragment
}
}
fragment SpecificPostFragment on SpecificPost {
owner {
id
name
}
}
fragment PostFragment on Post {
id
object
... on SpecificPost {
...SpecificPostFragment 
}
}

我试着知道是否：

1. 请求字段对象
2. 请求字段所有者

我尝试应用此处所写的内容：https://www.graphql-java.com/documentation/v11/fieldselection/

但是dataFetchingEnvironment.getSelectionSet().contains("XXX")似乎不能很好地处理碎片。如何做到这一点？

Answer 1

我还没有找到任何内置的解决方案，所以我编写了自己的解决方案。这是我的代码

import java.util.List;
import java.util.Objects;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import graphql.execution.MergedField;
import graphql.language.Field;
import graphql.language.FragmentDefinition;
import graphql.language.FragmentSpread;
import graphql.language.InlineFragment;
import graphql.language.SelectionSet;
import graphql.schema.DataFetchingEnvironment;
public class GraphQLUtil {
private static class PathElement {
private final String name;
private final String typeName;
public PathElement(String name, String typeName) {
this.name = name;
this.typeName = typeName;
}
public String getName() {
return name;
}
public String getTypeName() {
return typeName;
}
}
public static boolean containsIncludingFragments(DataFetchingEnvironment env, String path) {
Objects.requireNonNull(env, "The data fetching environment must not be null");
Objects.requireNonNull(path, "The field path must not be null");
List<PathElement> elts = Stream.of(path.split("/")).map(p -> {
String pt = p.trim();
if (pt.isEmpty()) {
throw new IllegalArgumentException("Empty path element found");
}
int sepIdx = pt.indexOf(":");
String name = pt;
String typeName = null;
if (sepIdx >= 0) {
typeName = pt.substring(0, sepIdx);
name = pt.substring(sepIdx + 1, pt.length());
}
return new PathElement(name, typeName);
}).collect(Collectors.toList());
if (elts.isEmpty()) {
return false;
}
MergedField mf = env.getMergedField();
return searchPathElement(env, elts, 0, mf.getSingleField().getSelectionSet(), null);
}
private static boolean searchPathElement(
DataFetchingEnvironment env,
List<PathElement> elts,
int eltIndex,
SelectionSet selectionSet,
String selectionTypeName) {
if (eltIndex >= elts.size()) {
return true;
}
PathElement currentElt = elts.get(eltIndex);
String currentName = currentElt.getName();
String currentTypeName = currentElt.getTypeName();
List<Field> fields = selectionSet.getSelectionsOfType(Field.class);
boolean found = false;
for (Field f : fields) {
if (f.getName().equals(currentName) && (currentTypeName == null
|| selectionTypeName == null
|| currentTypeName.equals(selectionTypeName))) {
found = searchPathElement(env, elts, eltIndex + 1, f.getSelectionSet(), null);
if (found) {
return true;
}
}
}
List<FragmentSpread> fragments = selectionSet.getSelectionsOfType(FragmentSpread.class);
for (FragmentSpread f : fragments) {
FragmentDefinition fDef = env.getFragmentsByName().get(f.getName());
found = searchPathElement(env, elts, eltIndex, fDef.getSelectionSet(), fDef.getTypeCondition().getName());
if (found) {
return true;
}
}
List<InlineFragment> inlineFragments = selectionSet.getSelectionsOfType(InlineFragment.class);
for (InlineFragment f : inlineFragments) {
found = searchPathElement(env, elts, eltIndex, f.getSelectionSet(), f.getTypeCondition().getName());
if (found) {
return true;
}
}
return false;
}
}

你这样称呼它：

DataFetchingEnvironment dataEnv = ... // If like me you use GraphQL SPQR, you can get it with io.leangen.graphql.execution.ResolutionEnvironment
boolean t1= GraphQLUtil.containsIncludingFragments(dataEnv, "id");
boolean t2 = GraphQLUtil.containsIncludingFragments(dataEnv, "owner/id");
boolean t3 = GraphQLUtil.containsIncludingFragments(dataEnv, "SpecificPost:owner/id"); // You may give the type of the field, if in some inheritance scenario, it is ambiguous

请注意，此解决方案不支持通配符(*或？(。如果主查询包含多个条目(例如，同一查询中的getPost+getPeople(，我还没有测试过它，但在这种情况下可能不起作用。