Ekiras Blogs: Filter

SpringBoot : How to create a Filter in Spring Boot Application

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Points To Remember

Implement the class Filter.
Add @Configuration annotation to the class to register it as a filter bean.
Call method

filterChain.doFilter(resquest,response) to continue the request flow

Call method sendError to send error,

((HttpServletResponse)response).sendError(HttpServletResponse.SC_BAD_REQUEST);

Call method sendRedirect to redirect request to error handler
```
((HttpServletResponse)response).sendRedirect("/errorUrl");
```

How to create a Filter in Spring Boot Application

IN order to make a filter, we have create a class SecurityFilter

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package com.ekiras.filter;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* @author ekansh
*/
@Component
@Order(Ordered.HIGHEST_PRECEDENCE)
public class SecurityFilter implements Filter {
private static final boolean CONDITION = true;
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
if(CONDITION==true)
chain.doFilter(request,response);
else{
((HttpServletResponse)response).setStatus(HttpServletResponse.SC_BAD_REQUEST);
}
}
@Override
public void destroy() {
}
}

package com.ekiras.filter;

import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @author ekansh
 */
@Component
@Order(Ordered.HIGHEST_PRECEDENCE)
public class SecurityFilter implements Filter {

    private static final boolean CONDITION = true;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        if(CONDITION==true)
            chain.doFilter(request,response);
        else{
            ((HttpServletResponse)response).setStatus(HttpServletResponse.SC_BAD_REQUEST);
        }

    }

    @Override
    public void destroy() {

    }
}

This is how you can create the filter and register it in the Spring Boot Application.

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SpringBoot : Read JSON object from POST Request in Filter

By Ekansh Rastogi

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0 Comments

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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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
}
}

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);

Ekiras Blogs

SpringBoot : How to create a Filter in Spring Boot Application

Points To Remember

How to create a Filter in Spring Boot Application

SpringBoot : Read JSON object from POST Request in Filter

Points To Remember

Read JSON in Filter and bind it to POJO class

Spring Boot : How to register a Filter in the Application

Steps : How to register a Filter in the Application

Spring : How to define Filter order in Filter Chain in Spring Boot

Points To Remember

How to define Filter order in Filter Chain in Spring Boot

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