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A Java implementation of the JSON Schema specification.
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package xpertss.json.schema.examples;
import com.fasterxml.jackson.databind.JsonNode;
import com.github.fge.jackson.NodeType;
import com.github.fge.jackson.jsonpointer.JsonPointer;
import xpertss.json.schema.cfg.ValidationConfiguration;
import xpertss.json.schema.core.exceptions.ProcessingException;
import xpertss.json.schema.core.keyword.syntax.checkers.AbstractSyntaxChecker;
import xpertss.json.schema.core.keyword.syntax.checkers.SyntaxChecker;
import xpertss.json.schema.core.processing.Processor;
import xpertss.json.schema.core.report.ProcessingReport;
import xpertss.json.schema.core.tree.SchemaTree;
import xpertss.json.schema.keyword.digest.AbstractDigester;
import xpertss.json.schema.keyword.digest.Digester;
import xpertss.json.schema.keyword.digest.helpers.IdentityDigester;
import xpertss.json.schema.keyword.digest.helpers.SimpleDigester;
import xpertss.json.schema.keyword.validator.AbstractKeywordValidator;
import xpertss.json.schema.keyword.validator.KeywordValidator;
import xpertss.json.schema.library.DraftV4Library;
import xpertss.json.schema.library.Keyword;
import xpertss.json.schema.library.KeywordBuilder;
import xpertss.json.schema.library.Library;
import xpertss.json.schema.library.LibraryBuilder;
import xpertss.json.schema.main.JsonSchema;
import xpertss.json.schema.main.JsonSchemaFactory;
import xpertss.json.schema.messages.JsonSchemaValidationBundle;
import xpertss.json.schema.processors.data.FullData;
import com.github.fge.msgsimple.bundle.MessageBundle;
import com.github.fge.msgsimple.load.MessageBundles;
import com.github.fge.msgsimple.source.MapMessageSource;
import com.github.fge.msgsimple.source.MessageSource;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import java.io.IOException;
import java.math.BigInteger;
import java.util.Collection;
import java.util.Comparator;
import java.util.List;
import java.util.Set;
import java.util.SortedSet;
/**
* Ninth example: augmenting schemas with custom keywords
*
*
*
*
*
* This example adds a custom keyword with syntax checking, digesting and
* keyword validation. The chosen keyword is {@code divisors}: it applies to
* integer values and takes an array of (unique) integers as an argument.
*
* The validation is the same as for {@code multipleOf} except that it is
* restricted to integer values and the instance must be a multiple of all
* divisors. For instance, if the value of this keyword is {@code [2, 3]}, then
* 6 validates successfully but 14 does not (it is divisible by 2 but not 3).
*
*
* For this, you need to create your own keyword. This is done using {@link
* Keyword#newBuilder(String)}, where the argument is the name of your keyword,
* and then add the following elements:
*
*
* - a {@link SyntaxChecker} (using {@link
* KeywordBuilder#withSyntaxChecker(SyntaxChecker)};
* - a {@link Digester} (using {@link
* KeywordBuilder#withDigester(Digester)};
* - and finally, a {@link KeywordValidator} (using {@link
* KeywordBuilder#withValidatorClass(Class)}.
*
*
* Then, as in {@link Example8}, you need to get hold of a {@link Library}
* (we choose again to extend the draft v4 library) and add the (frozen)
* keyword to it using {@link LibraryBuilder#addKeyword(Keyword)}.
*
* The keyword validator must have a single constructor taking a
* {@link JsonNode} as an argument (which will be the result of the {@link
* Digester}). Note that you may omit to write a digester and choose instead to
* use an {@link IdentityDigester} or a {@link SimpleDigester} (which you inject
* into a keyword using {@link
* KeywordBuilder#withIdentityDigester(NodeType, NodeType...)} and {@link
* KeywordBuilder#withSimpleDigester(NodeType, NodeType...)} respectively).
*
* Two sample files are given: the first (link) is valid, the other (link) isn't (the first and third
* elements fail to divide by one or more factors).
*/
public final class Example9
{
public static void main(final String... args)
throws IOException, ProcessingException
{
final JsonNode customSchema = Utils.loadResource("/custom-keyword.json");
final JsonNode good = Utils.loadResource("/custom-keyword-good.json");
final JsonNode bad = Utils.loadResource("/custom-keyword-bad.json");
/*
* Build the new keyword
*/
final Keyword keyword = Keyword.newBuilder("divisors")
.withSyntaxChecker(DivisorsSyntaxChecker.getInstance())
.withDigester(DivisorsDigesters.getInstance())
.withValidatorClass(DivisorsKeywordValidator.class).freeze();
/*
* Build a library, based on the v4 library, with this new keyword
*/
final Library library = DraftV4Library.get().thaw()
.addKeyword(keyword).freeze();
/*
* Complement the validation message bundle with a dedicated message
* for our keyword validator
*/
final String key = "missingDivisors";
final String value = "integer value is not a multiple of all divisors";
final MessageSource source = MapMessageSource.newBuilder()
.put(key, value).build();
final MessageBundle bundle
= MessageBundles.getBundle(JsonSchemaValidationBundle.class)
.thaw().appendSource(source).freeze();
/*
* Build a custom validation configuration: add our custom library and
* message bundle
*/
final ValidationConfiguration cfg = ValidationConfiguration.newBuilder()
.setDefaultLibrary("http://my.site/myschema#", library)
.setValidationMessages(bundle).freeze();
final JsonSchemaFactory factory = JsonSchemaFactory.newBuilder()
.setValidationConfiguration(cfg).freeze();
final JsonSchema schema = factory.getJsonSchema(customSchema);
ProcessingReport report;
report = schema.validate(good);
System.out.println(report);
report = schema.validate(bad);
System.out.println(report);
}
/*
* Our custom syntax checker
*/
private static final class DivisorsSyntaxChecker
extends AbstractSyntaxChecker
{
private static final SyntaxChecker INSTANCE
= new DivisorsSyntaxChecker();
public static SyntaxChecker getInstance()
{
return INSTANCE;
}
private DivisorsSyntaxChecker()
{
/*
* When constructing, the name for the keyword must be provided
* along with the allowed type for the value (here, an array).
*/
super("divisors", NodeType.ARRAY);
}
@Override
protected void checkValue(final Collection pointers,
final MessageBundle bundle, final ProcessingReport report,
final SchemaTree tree)
throws ProcessingException
{
/*
* Using AbstractSyntaxChecker as a base, we know that when we reach
* this method, the value has already been validated as being of
* the allowed primitive types (only array here).
*
* But this is not enough for this particular validator: we must
* also ensure that all elements of this array are integers. Cycle
* through all elements of the array and check each element. If we
* encounter a non integer argument, add a message.
*
* We must also check that there is at lease one element, that the
* array contains no duplicates and that all elements are positive
* integers and strictly greater than 0.
*
* The getNode() method grabs the value of this keyword for us, so
* use that. Note that we also reuse some messages already defined
* in SyntaxMessages.
*/
final JsonNode node = getNode(tree);
final int size = node.size();
if (size == 0) {
report.error(newMsg(tree, bundle, "emptyArray"));
return;
}
NodeType type;
JsonNode element;
boolean uniqueItems = true;
final Set set = Sets.newHashSet();
for (int index = 0; index < size; index++) {
element = node.get(index);
type = NodeType.getNodeType(element);
if (type != NodeType.INTEGER)
report.error(newMsg(tree, bundle, "incorrectElementType")
.put("expected", NodeType.INTEGER)
.put("found", type));
else if (element.bigIntegerValue().compareTo(BigInteger.ONE) < 0)
report.error(newMsg(tree, bundle, "integerIsNegative")
.put("value", element));
uniqueItems = set.add(element);
}
if (!uniqueItems)
report.error(newMsg(tree, bundle, "elementsNotUnique"));
}
}
/*
* Our custom digester
*
* We take the opportunity to build a digested form where, for instance,
* [ 3, 5 ] and [ 5, 3 ] give the same digest.
*/
private static final class DivisorsDigesters
extends AbstractDigester
{
private static final Digester INSTANCE = new DivisorsDigesters();
public static Digester getInstance()
{
return INSTANCE;
}
private DivisorsDigesters()
{
super("divisors", NodeType.INTEGER);
}
@Override
public JsonNode digest(final JsonNode schema)
{
final SortedSet set = Sets.newTreeSet(COMPARATOR);
for (final JsonNode element: schema.get(keyword))
set.add(element);
return FACTORY.arrayNode().addAll(set);
}
/*
* Custom Comparator. We compare BigInteger values, since all integers
* are representable using this class.
*/
private static final Comparator COMPARATOR
= new Comparator()
{
@Override
public int compare(final JsonNode o1, final JsonNode o2)
{
return o1.bigIntegerValue().compareTo(o2.bigIntegerValue());
}
};
}
/**
* Custom keyword validator for {@link Example9}
*
* It must be {@code public} because it is built by reflection.
*/
public static final class DivisorsKeywordValidator
extends AbstractKeywordValidator
{
/*
* We want to validate arbitrarily large integer values, we therefore
* use BigInteger.
*/
private final List divisors;
public DivisorsKeywordValidator(final JsonNode digest)
{
super("divisors");
final ImmutableList.Builder list
= ImmutableList.builder();
for (final JsonNode element: digest)
list.add(element.bigIntegerValue());
divisors = list.build();
}
@Override
public void validate(final Processor processor,
final ProcessingReport report, final MessageBundle bundle,
final FullData data)
throws ProcessingException
{
final BigInteger value
= data.getInstance().getNode().bigIntegerValue();
/*
* We use a plain list to store failed divisors: remember that the
* digested form was built with divisors in order, we therefore
* only need insertion order, and a plain ArrayList guarantees that.
*/
final List failed = Lists.newArrayList();
for (final BigInteger divisor: divisors)
if (!value.mod(divisor).equals(BigInteger.ZERO))
failed.add(divisor);
if (failed.isEmpty())
return;
/*
* There are missed divisors: report.
*/
report.error(newMsg(data, bundle, "missingDivisors")
.put("divisors", divisors).put("failed", failed));
}
@Override
public String toString()
{
return "divisors: " + divisors;
}
}
}