add support for maxItems keyword

core/pom.xml

@@ -116,6 +116,7 @@
                                         <inculde>**/tests/draft2020-12/items.json</inculde>
                                         -->
                                         <inculde>**/tests/draft2020-12/minItems.json</inculde>
+                                        <inculde>**/tests/draft2020-12/maxItems.json</inculde>
                                     </includes>
                                 </resource>
                             </resources>

core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/MaxItemsKeywordType.java

@@ -0,0 +1,65 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2023 sebastian.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package io.github.sebastiantoepfer.jsonschema.core.vocab.validation;
+
+import io.github.sebastiantoepfer.jsonschema.InstanceType;
+import io.github.sebastiantoepfer.jsonschema.JsonSchema;
+import io.github.sebastiantoepfer.jsonschema.keyword.Assertion;
+import io.github.sebastiantoepfer.jsonschema.keyword.Keyword;
+import io.github.sebastiantoepfer.jsonschema.keyword.KeywordType;
+import jakarta.json.JsonNumber;
+import jakarta.json.JsonValue;
+import java.util.Objects;
+
+final class MaxItemsKeywordType implements KeywordType {
+
+    @Override
+    public String name() {
+        return "maxItems";
+    }
+
+    @Override
+    public Keyword createKeyword(final JsonSchema schema, final JsonValue value) {
+        return new MaxItemsKeyword((JsonNumber) value);
+    }
+
+    private class MaxItemsKeyword implements Assertion {
+
+        private final int maxItems;
+
+        public MaxItemsKeyword(final JsonNumber maxItems) {
+            this.maxItems = maxItems.intValue();
+        }
+
+        @Override
+        public boolean isValidFor(final JsonValue instance) {
+            return !InstanceType.ARRAY.isInstance(instance) || instance.asJsonArray().size() <= maxItems;
+        }
+
+        @Override
+        public boolean hasName(final String name) {
+            return Objects.equals(name(), name);
+        }
+    }
+}

core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/ValidationVocabulary.java

@@ -46,7 +46,8 @@ public ValidationVocabulary() {
                 new MaximumKeywordType(),
                 new ExclusiveMaximumKeywordType(),
                 new MultipleOfKeywordType(),
-                new MinItemsKeywordType()
+                new MinItemsKeywordType(),
+                new MaxItemsKeywordType()
             );
     }
 

core/src/test/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/MaxItemsKeywordTypeTest.java

@@ -0,0 +1,89 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2023 sebastian.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package io.github.sebastiantoepfer.jsonschema.core.vocab.validation;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+
+import io.github.sebastiantoepfer.jsonschema.core.DefaultJsonSchemaFactory;
+import io.github.sebastiantoepfer.jsonschema.keyword.Keyword;
+import jakarta.json.Json;
+import jakarta.json.JsonValue;
+import org.junit.jupiter.api.Test;
+
+class MaxItemsKeywordTypeTest {
+
+    @Test
+    void should_know_his_name() {
+        final Keyword keyword = new MaxItemsKeywordType()
+            .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), Json.createValue(1));
+
+        assertThat(keyword.hasName("maxItems"), is(true));
+        assertThat(keyword.hasName("test"), is(false));
+    }
+
+    @Test
+    void should_be_valid_for_non_arrays() {
+        assertThat(
+            new MaxItemsKeywordType()
+                .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), Json.createValue(2))
+                .asAssertion()
+                .isValidFor(JsonValue.EMPTY_JSON_OBJECT),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_valid_for_array_with_same_size() {
+        assertThat(
+            new MaxItemsKeywordType()
+                .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), Json.createValue(2))
+                .asAssertion()
+                .isValidFor(Json.createArrayBuilder().add(1).add(2).build()),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_valid_for_array_with_smaller_size() {
+        assertThat(
+            new MaxItemsKeywordType()
+                .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), Json.createValue(2))
+                .asAssertion()
+                .isValidFor(Json.createArrayBuilder().add(1).build()),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_invalid_for_array_with_greather_size() {
+        assertThat(
+            new MaxItemsKeywordType()
+                .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), Json.createValue(2))
+                .asAssertion()
+                .isValidFor(Json.createArrayBuilder().add(1).add(2).add(3).build()),
+            is(false)
+        );
+    }
+}