{"id":78579,"date":"2020-09-20T06:25:33","date_gmt":"2020-09-20T06:25:33","guid":{"rendered":"https:\/\/www.baeldung.com\/?p=87377"},"modified":"2020-09-20T06:25:33","modified_gmt":"2020-09-20T06:25:33","slug":"json-parameters-with-spring-mvc","status":"publish","type":"post","link":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/2020\/09\/20\/json-parameters-with-spring-mvc\/","title":{"rendered":"JSON Parameters with Spring MVC"},"content":{"rendered":"

<\/p>\n

1. Overview<\/h2>\n
<\/div>\n

In this short tutorial, we’re going to take a close look at how to work with JSON parameters in Spring MVC.<\/p>\n

First, we’ll start with a little bit\u00a0of\u00a0background on JSON parameters. Then, we’ll go down the rabbit hole to see how to send JSON parameters in POST and GET requests.<\/p>\n

2. JSON Parameters in Spring MVC<\/h2>\n
<\/div>\n

Using JSON<\/a> to send or receive data is a common practice among web developers. The hierarchical structure of the JSON strings offers a more compact and human-readable way to represent HTTP request parameters.<\/p>\n

By default, Spring MVC provides out-of-the-box data binding for simple data types such as String<\/em>. For that purpose, it uses a list of built-in property editors<\/a> under-the-hood.<\/strong><\/p>\n

However, in real-world projects, we may want to bind more complex data types. For example, it might be handy to be able to map a JSON parameter into a model object.<\/p>\n

3. Send JSON Data in POST<\/h2>\n
<\/div>\n

Spring provides a straightforward way to send JSON data via POST requests. The built-in @RequestBody <\/em>annotation<\/a> can\u00a0automatically deserialize the JSON data encapsulated in the request body into a particular model object.<\/p>\n

In general, we don’t have to parse the request body ourselves. We can use the Jackson library<\/a> to do all the heavy lifting for us<\/strong>.<\/p>\n

Now, let’s see how to send JSON data via a POST request in Spring MVC.<\/p>\n

Firstly, we need to create a model object to represent the passed JSON data. For instance, consider the Product<\/em> class:<\/p>\n

public class Product {\r\n    private int id;\r\n    private String name;\r\n    private double price;\r\n    \/\/ default constructor + getters + setters\r\n}<\/code><\/pre>\n
Secondarily, let’s define a Spring handler method that accepts POST requests:<\/p>\n
@PostMapping(\"\/create\")\r\n@ResponseBody\r\npublic Product createProduct(@RequestBody Product product) {\r\n    \/\/ custom logic\r\n    return product;\r\n}<\/code><\/pre>\n
As we can see, annotating the product <\/em>argument with @RequestBody<\/em> is enough to bind the JSON data sent from the clients<\/strong>.<\/p>\n
Now, we can test our POST request using cURL<\/a>:<\/p>\n
curl -i \\\r\n-H \"Accept: application\/json\" \\\r\n-H \"Content-Type: application\/json\" \\\r\n-X POST --data \\\r\n  '{\"id\": 1,\"name\": \"Asus Zenbook\",\"price\": 800}' \"http:\/\/localhost:8080\/spring-mvc-basics-4\/products\/create\"<\/code><\/pre>\n
4. Send JSON Parameter in GET<\/h2>\n
<\/div>\n
Spring MVC offers @RequestParam<\/em><\/a> to extract query parameters from GET requests. However, unlike @RequestBody, <\/em>the @RequestParam <\/em>annotation supports only simple data types such as int<\/em> and String<\/em>.<\/p>\n
So, to send JSON, we’ll need to define our JSON parameter as a simple string.<\/p>\n
The big question here is: How do we convert our JSON parameter (which is a String<\/em>) into an object of the Product<\/em> class?<\/p>\n
The answer is pretty simple! The ObjectMapper<\/em> class<\/a> provided by the Jackson library offers a flexible way to convert JSON strings into Java objects<\/strong>.<\/p>\n
Now, let’s see how to send a JSON parameter via a GET request in Spring MVC. First, we’ll need to create another handler method in our controller to handle GET requests:<\/p>\n
@GetMapping(\"\/get\")\r\n@ResponseBody\r\npublic Product getProduct(@RequestParam String product) throws JsonMappingException, JsonProcessingException {\r\n    Product prod = objectMapper.readValue(product, Product.class);\r\n    return prod;\r\n}<\/code><\/pre>\n
As shown above, the readValue()<\/em> method allows deserializing the JSON parameter product<\/em> directly into an instance of the Product<\/em> class.<\/p>\n
Note that we define our JSON query parameter as a String<\/em> object. Now, what if we want to pass a Product<\/em> object like we did when using @RequestBody<\/em>?<\/p>\n
To answer this question, Spring provides a concise and flexible solution through custom property editors<\/a>.<\/p>\n
First, we’ll need to create a custom property editor to encapsulate the logic of converting the JSON parameter given as a String<\/em> to a Product\u00a0<\/em>object<\/strong>:<\/p>\n
public class ProductEditor extends PropertyEditorSupport {\r\n    private ObjectMapper objectMapper;\r\n    public ProductEditor(ObjectMapper objectMapper) {\r\n        this.objectMapper = objectMapper;\r\n    }\r\n    @Override\r\n    public void setAsText(String text) throws IllegalArgumentException {\r\n        if (StringUtils.isEmpty(text)) {\r\n            setValue(null);\r\n        } else {\r\n            Product prod = new Product();\r\n            try {\r\n                prod = objectMapper.readValue(text, Product.class);\r\n            } catch (JsonProcessingException e) {\r\n                throw new IllegalArgumentException(e);\r\n            }\r\n            setValue(prod);\r\n        }\r\n    }\r\n}<\/code><\/pre>\n
Next, let’s bind the JSON parameter to an object of Product<\/em> class:<\/p>\n
@GetMapping(\"\/get2\")\r\n@ResponseBody\r\npublic Product get2Product(@RequestParam Product product) {\r\n    \/\/ custom logic\r\n    return product;\r\n}<\/code><\/pre>\n
Lastly, we need to add the last missing piece of the puzzle. Let’s register ProductEditor<\/em> in our Spring controller<\/strong>:<\/p>\n
@InitBinder\r\npublic void initBinder(WebDataBinder binder) {\r\n    binder.registerCustomEditor(Product.class, new ProductEditor(objectMapper));\r\n}<\/code><\/pre>\n
Bear in mind that we need to URL-encode the JSON parameter to ensure safe transport<\/strong>.<\/p>\n
So, instead of:<\/p>\n
GET \/spring-mvc-basics-4\/products\/get2?product={\"id\": 1,\"name\": \"Asus Zenbook\",\"price\": 800}<\/code><\/pre>\n
We need to send:<\/p>\n
GET \/spring-mvc-basics-4\/products\/get2?product=%7B%22id%22%3A%201%2C%22name%22%3A%20%22Asus%20Zenbook%22%2C%22price%22%3A%20800%7D<\/code><\/pre>\n
5. Conclusion<\/h2>\n
<\/div>\n
To sum it up, we saw how to work with JSON in Spring MVC. Along the way, we showcased how to send JSON parameters in POST and GET requests.<\/p>\n
As always, the full source code of the examples is available over on GitHub<\/a>.<\/p>\n
The post JSON Parameters with Spring MVC<\/a> first appeared on Baeldung<\/a>.<\/p>\n
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Learn how to send JSON parameters in GET and POST requests when using Spring MVC.<\/p>\n
The post JSON Parameters with Spring MVC<\/a> first appeared on Baeldung<\/a>.<\/p>\n
<\/a> <\/a> <\/a> <\/a> <\/a> <\/a> <\/a> <\/a> <\/div>\n<\/div>","protected":false},"author":792,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"slim_seo":{"title":"JSON Parameters with Spring MVC - ITTeacherITFreelance.hk","description":"Learn how to send JSON parameters in GET and POST requests when using Spring MVC. The post JSON Parameters with Spring MVC first appeared on Baeldung .   &"},"footnotes":""},"categories":[6],"tags":[5358],"_links":{"self":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/78579"}],"collection":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/users\/792"}],"replies":[{"embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/comments?post=78579"}],"version-history":[{"count":7,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/78579\/revisions"}],"predecessor-version":[{"id":81747,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/posts\/78579\/revisions\/81747"}],"wp:attachment":[{"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/media?parent=78579"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/categories?post=78579"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itteacheritfreelance.hk\/wordpress\/index.php\/wp-json\/wp\/v2\/tags?post=78579"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}