jackson | 易学教程

Simple Jackson deserialization of nested objects

阅读更多关于 Simple Jackson deserialization of nested objects

问题 This should be trivial but for some reason I can't seem to get it right. I have the following JSON response { "info": "processing", "data": { "id": "123", "cars": [ { "id": "1" }, { "id": "2" } ] } } I've tried converting it with simple POJO's @JsonRootName(value = "data") public class Product { String id; List<Car> cars; } And public class Car { String id; } But that returns an empty Product object with the id and products null. Surely I don't need to write a custom JsonDeserialize for this

Android+Java Web+MySQL实现登录注册

阅读更多关于 Android+Java Web+MySQL实现登录注册

1 前言&概述这篇文章是基于此处文章的更新，更新了一些技术栈，更加贴近实际需要，以及修复了若干的错误。这是一个前端 Android +后端 Java/Kotlin 通过 Servelt 进行后台数据库（ MySQL ）交互的详细步骤以及源码实现，技术栈： Android 基础原生 JDBC +原生 Servlet Tomcat + MySQL （ Docker ）当然现在的很多 Java 后端开发都使用了 Spring Boot 而不是原生的 Servlet ，所以使用 Spring Boot 实现的可以笔者的另一篇文章。尽管基于 Spring Boot 实现非常的简便，但是使用原生的 Servlet 更能理解底层的原理。另外本篇文章是偏基础向的教程，很多步骤都会比较详细而且附上了图，好了废话不说，正文开始。 2 环境 Android Studio 4.1.2 IntelliJ IDEA 2020.3 MySQL 8.0.23 Tomcat 10.0 Docker 20.10.1 服务器 CentOS 8.1.1911 3 环境准备 3.1 IDE 准备官网安装 Android Studio + IDEA ，这部分就省略了。 3.2 MySQL 3.2.1 安装概述这里的 MySQL 若无特殊说明指的是 MySQL Community 。首先，在

How I parse Color java class to JSON with Jackson?

阅读更多关于 How I parse Color java class to JSON with Jackson?

问题 I am trying to deserialise the Color class from JSON with Jackson but it throws exception: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "colorSpace" (class java.awt.Color), not marked as ignorable. What i'm doing wrong? This is my code: File act = new File(new File().getAbsolutePath()); ObjectMapper om = new ObjectMapper(); File f = new File(act, "123.JSON"); om.writeValue(f, new person()); person per = om.readValue(f, person.class); System.out.println

Simple Jackson deserialization of nested objects

阅读更多关于 Simple Jackson deserialization of nested objects

Deserializing to object with overloaded setter with fasterxml.jackson

阅读更多关于 Deserializing to object with overloaded setter with fasterxml.jackson

问题 I want to deserialize json string into object which have overloaded setter for a field. I don't want to explicitly annotate one of the setter with @JsonIgnore. Why can't jackson library use appropriate setter according to the type of value it fetches in json string? Following is Code: public class A { Set<Integer> set = new HashSet<Integer>(); public Set<Integer> getSet() { return set; } public void setSet(Set<Integer> set) { this.set = set; } public void setSet(String str) { this.set = null;

Serializing Joda DateTime object is creating different output depending on context

阅读更多关于 Serializing Joda DateTime object is creating different output depending on context

问题 I have an object in which is nested a Joda DateTime object, and I'm having trouble serializing it and deserializing it. When I serialize the full object that DateTime is nested in, the output looks vastly different than when I serialize the DateTime object directly, my results are below new ObjectMapper.writeValueAsString(fullObjectWithDateTime) produces the following blob for the DateTime object: { "dateTime": { "weekOfWeekyear": 34, "weekyear": 2019, "yearOfEra": 2019, "yearOfCentury": 19,

Json to Java Mapping

阅读更多关于 Json to Java Mapping

问题 I want to map below Json data to java object of List<Map<String, String>> type. Sample Json: { { a:b, c:d }, { e:f, g:h, i:j }, { h:k } } Here a:b represents key-value pair. So a:b and c:d will be mapped to first map of the list and so on. one way to do this is by building JSON tree and access each node and store the pair into the map. Is there a better way to do this (cleaner approach)? 回答1: Here is the code to read a List<Map<String, String>> using the Jackson library, with your example

Jackson YAML: support for tags

阅读更多关于 Jackson YAML: support for tags

问题 I'm investigating the use of YAML for a somewhat complicated metadata language. One thing that would be of great use is if the YAML parser supported the use of YAML tags. This would allow people who write documents in this metadata language to indicate when/if they are defining some object with a well-defined schema. For example: set_one: !dset bass: tama rockstar 22x16 snare: ludwig supralight 6.5x15 tom1: tama rockstar 12x11 tom2: tama rockstar 16x16 The use of the "!dset" tag in the above

How to deserialize null type JSON fields with Jackson

阅读更多关于 How to deserialize null type JSON fields with Jackson

问题 I'm developing a PATCH API. If the fields are sent as JSON null value I need to save them as null . However I can't distinguish if they're sent as null or never sent. { "max_amount": null } Double maxAmount; I have Double , Integer , Date etc. fields. I can deserialize them to Double.NAN , Integer.MIN_VALUE when they're really sent as null to understand if they're sent as null . But Deserializers don't work when the field is null . Of course it's an option to send "-1" or an impossible value

Deserialize duplicate keys to list using Jackson

阅读更多关于 Deserialize duplicate keys to list using Jackson

问题 I'm trying to deserialize json into object. However, the json has duplicate keys. I cannot change the json and I would like to use Jackson to change duplicate keys to a list. Here is an example of the json I retrieve: { "myObject": { "foo": "bar1", "foo": "bar2" } } And here is what I would like after deserialization: { "myObject": { "foo": ["bar1","bar2"] } } I created my class like so: public class MyObject { private List<String> foo; // constructor, getter and setter } I tried to use