Without setting `@JsonCreator` for the POJO, the `required` attribute in `@JsonProperty` is not checked

[linghengqian]

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TL;

• While investigating Removes use of JAXB API via jackson-dataformat-xml apache/shardingsphere#29384 , I noticed that without setting @JsonCreator for the POJO, the required attribute in @JsonProperty is not checked.

• I created a minimal unit test at https://github.com/linghengqian/jackson-xml-required-check-test . The core code looks like this.

public class RequiredTest {
    @Test
    void assertRequiredValue() {
        ObjectMapper XML_MAPPER = XmlMapper.builder().build();
        assertThrows(MismatchedInputException.class, () -> XML_MAPPER.readValue("<Record></Record>", TestRecord.class));
        assertThrows(MismatchedInputException.class, () -> XML_MAPPER.readValue("<TR></TR>", TestRecordWithoutCreator.class));
    }

    @Getter
    @NoArgsConstructor
    @JacksonXmlRootElement(localName = "Record")
    static class TestRecord {
        private String type;

        private String driverClassName;

        @JsonCreator
        public TestRecord(
                @JsonProperty(required = true) @JacksonXmlProperty(localName = "type", isAttribute = true)
                String type,
                @JsonProperty(required = true) @JacksonXmlProperty(localName = "driverClassName")
                String driverClassName) {
            this.type = type;
            this.driverClassName = driverClassName;
        }
    }

    @Getter
    @JacksonXmlRootElement(localName = "TR")
    static class TestRecordWithoutCreator {
        @JsonProperty(required = true)
        @JacksonXmlProperty(localName = "type", isAttribute = true)
        private String type;

        @JsonProperty(required = true)
        @JacksonXmlProperty(localName = "driverClassName")
        private String driverClassName;
    }
}

• assertThrows(MismatchedInputException.class, () -> XML_MAPPER.readValue("<TR></TR>", TestRecordWithoutCreator.class)); will not throw any exception.

[ERROR] com.lingh.RequiredTest.assertRequiredValue -- Time elapsed: 0.276 s <<< FAILURE!
org.opentest4j.AssertionFailedError: Expected com.fasterxml.jackson.databind.exc.MismatchedInputException to be thrown, but nothing was thrown.
        at org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:152)
        at org.junit.jupiter.api.AssertThrows.assertThrows(AssertThrows.java:73)
        at org.junit.jupiter.api.AssertThrows.assertThrows(AssertThrows.java:35)
        at org.junit.jupiter.api.Assertions.assertThrows(Assertions.java:3115)
        at com.lingh.RequiredTest.assertRequiredValue(RequiredTest.java:21)
        at java.base/java.lang.reflect.Method.invoke(Method.java:568)
        at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
        at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

• Did I misunderstand something while reading the documentation?

[cowtowncoder]

Correct: @JsonProperty(required=true) is only enforced if and when properties are passed via Creator method (constructor or static factory method). It would be nice to support if for Setter/Field injected properties too; it is one of "most-wanted" issues:

FasterXML/jackson-databind#230

Closing this as duplicate (also note: this is not XML-specific issue but same for all backends).