asmhatre
c438afc33b
37 runnable examples covering the eight feature posts on ankurm.com, verified against Jackson 3.2.1 on Temurin 21.0.5. Every output committed under docs/ was produced by run-all.sh. Also documents 11 places where the published snippets do not compile or do not behave as printed against a real Jackson 3 build - most notably that writeValueAsString(List<Base>) silently drops the polymorphic type discriminator, so the post's serialised output cannot be read back.
36 lines
1.4 KiB
Java
36 lines
1.4 KiB
Java
package com.ankurm.jackson3.part4custom;
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import tools.jackson.core.JsonParser;
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import tools.jackson.databind.DeserializationContext;
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import tools.jackson.databind.JsonNode;
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import tools.jackson.databind.deser.std.StdDeserializer;
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import java.math.BigDecimal;
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/**
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* Post: Custom Serialisers and Mix-ins — https://ankurm.com/jackson-custom-serializer-mixin/
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* Section: "Writing a Custom Deserialiser"
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*
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* Jackson 3 differences from the post's code:
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* 1. jsonParser.getCodec().readTree(jsonParser) is gone. Use ctxt.readTree(parser).
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* 2. No `throws IOException` — JacksonException is unchecked.
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* 3. path() rather than get(), so a missing field yields a MissingNode instead of
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* a NullPointerException. The post's version NPEs on {"currency":"USD"}.
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* 4. A bare decimalValue() on a MissingNode THROWS in Jackson 3 (it returned
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* BigDecimal.ZERO in Jackson 2). Use the defaulting overload.
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*/
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public class E02MoneyValueDeserializer extends StdDeserializer<Money> {
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public E02MoneyValueDeserializer() {
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super(Money.class);
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}
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@Override
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public Money deserialize(JsonParser jsonParser, DeserializationContext ctxt) {
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JsonNode rootNode = ctxt.readTree(jsonParser);
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BigDecimal amount = rootNode.path("amount").decimalValue(BigDecimal.ZERO);
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String currency = rootNode.path("currency").asString("GBP"); // default when absent
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return new Money(amount, currency);
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}
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}
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