SpringBoot : Read JSON object from POST Request in Filter

Points To Remember

Add the following dependency to the gradle project.

compile('com.fasterxml.jackson.core:jackson-databind:2.7.1-1')

Read JSON in Filter and bind it to POJO class

You can read the JSON inside a Filter class in SpringBoot by 

• Create a BufferedReader object by reading request object.
• Create an ObjectMapper object.
• Read JSON from bufferedReader object and bind it to any POJO class.

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1. package com.ekiras.test;  
2.   
3. import com.fasterxml.jackson.databind.JsonMappingException;  
4. import com.fasterxml.jackson.databind.ObjectMapper;  
5.   
6. import javax.servlet.*;  
7. import java.io.BufferedReader;  
8. import java.io.IOException;  
9.   
10. /** 
11.  * @author ekansh 
12.  * @since 26/3/16 
13.  */  
14. public class MyFilter implements Filter {  
15.   
16.   
17.     @Override  
18.     public void init(FilterConfig filterConfig) throws ServletException {  
19.         // some init code   
20.     }  
21.   
22.     @Override  
23.     public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {  
24.         // declare a reader    
25.         BufferedReader reader;  
26.         try{  
27.             // get reader from the request object  
28.             reader = request.getReader();  
29.             // create an object mapper instance  
30.             ObjectMapper mapper = new ObjectMapper();  
31.             // read values from the reader object and map the response to desired class.  
32.             mapper.readValue(reader,Object.class);  
33.         }catch (JsonMappingException e){  
34.             e.printStackTrace();  
35.         }  
36.     }  
37.   
38.     @Override  
39.     public void destroy() {  
40.         // some code to be run at destruction  
41.     }  
42.   
43. }  

package com.ekiras.test; import com.fasterxml.jackson.databind.JsonMappingException; import com.fasterxml.jackson.databind.ObjectMapper; import javax.servlet.*; import java.io.BufferedReader; import java.io.IOException; /** * @author ekansh * @since 26/3/16 */ public class MyFilter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { // some init code } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { // declare a reader BufferedReader reader; try{ // get reader from the request object reader = request.getReader(); // create an object mapper instance ObjectMapper mapper = new ObjectMapper(); // read values from the reader object and map the response to desired class. mapper.readValue(reader,Object.class); }catch (JsonMappingException e){ e.printStackTrace(); } } @Override public void destroy() { // some code to be run at destruction } }

So, in this way you can read JSON from the request and bind it to the any custom class.

Note :: To bind the JSON to any POJO class, you need to pass the class name of the pojo class to the objectMapper object.
e.g mapper.readValue(reader,MyCustomClass.class);