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Jackson usually throws Can not construct instance of java.time.LocalDate because the ObjectMapper doing the deserialization does not have Java time support registered. Add Jackson’s jackson-datatype-jsr310 module and register JavaTimeModule on that exact mapper. Then confirm the JSON date value matches the format the mapper expects.
Register JavaTimeModule on the mapper that fails
LocalDate belongs to Java’s java.time API. Jackson’s Java time module supplies a LocalDateDeserializer; merely having a configured mapper somewhere in the application does not help if the failing code uses a different one. The module’s source shows the manual registration pattern:
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JavaTimeModule());Add the jackson-datatype-jsr310 dependency to the application, using a version compatible with the other Jackson artifacts in the project. The module’s implementation and the LocalDateDeserializer API document the support it provides.
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Do not register a module on one mapper and assume it affects every mapper. Find the code that calls readValue (or the framework component that performs deserialization), then verify which mapper instance it actually uses.
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Check the JSON value and expected date format
With Java time support registered and timestamp serialization disabled, Jackson documents ISO-8601 strings as the standard representation. A typical date-only value is:
{"startDate":"2026-10-07"}Check the raw JSON token for the failing property, as well as mapper features and any property-level format configuration. The expected input can differ if the application has a custom date contract or format.
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Jackson documents a different representation when WRITE_DATES_AS_TIMESTAMPS is enabled: LocalDate and other local temporal types are represented as arrays, since they cannot be portably converted to timestamps. See the JavaTimeModule 2.22.1 API for that behavior. If a producer sends a non-ISO string, establish the actual input contract first; only then configure a matching field-level format or custom deserializer.
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| Mapper setup | Where Java time support belongs | What to verify |
|---|---|---|
| Manually constructed mapper | Register JavaTimeModule on the same ObjectMapper used to deserialize the payload. |
Search for independent new ObjectMapper() instances and check the one at the failing call site. |
| Spring Boot-managed mapper | Use the auto-configured mapper, which can receive Jackson module beans and modules found through Java ServiceLoader. | Confirm the component uses the framework-managed mapper, and check documentation for the application’s Spring Boot version. |
Spring Boot’s Spring MVC documentation describes automatic registration for its auto-configured JSON mapper setup. That configuration does not automatically apply to a separate mapper created by application code.
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Trace the error with a short diagnostic sequence
- Read the complete exception. Identify the property that Jackson was trying to deserialize and the exact call site or framework component involved.
- Check runtime dependencies. Confirm that
jackson-datatype-jsr310is present and that its version is compatible with the project’s Jackson core and databind artifacts. - Inspect the active mapper. Verify that Java time support is registered on the mapper performing the work. If the code constructs its own mapper, register the module there.
- Inspect the actual JSON. Check whether the property is a string, array, or another token, and compare it with the active mapper settings and any per-property format.
- Check framework versus custom configuration. In Spring Boot, determine whether the failing code uses the auto-configured mapper or an independently constructed one.
- Reduce the failure. Reproduce it with a minimal DTO and the smallest payload that still fails. Add a custom format or deserializer only if that reproduction confirms the input contract requires one.
Why the common fixes can miss the problem
- Adding the dependency alone: the application also needs the module registered on the mapper that performs deserialization.
- Configuring a framework mapper: a manually created mapper is a separate instance and may not inherit framework configuration.
- Changing the date pattern immediately: this will not correct missing Java time support, and may make the mapper expect a format the producer does not send.
- Registering modules everywhere: first identify the active mapper and its existing setup; duplicate or unrelated configuration obscures the actual cause.
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