Add/Modify Header Values in Java HttpServletRequest using Servlet Filters

Add/Modify Header Values in Java HttpServletRequest using Servlet Filters

Steps to Modify Request Headers in a Servlet Request.

This example will demonstrate how to modify 'Content-Type' header in Java Servlet Filter.

In order to achieve this, use a custom wrapper Class, that extends HttpServletRequestWrapper.

Thereafter, we need to override certain methods inside this custom Class.

• getHeader(String name)
• getHeaders(String name)
• getHeaderNames()
• getParameter(final String name)

Code snippet for overriding above methods.

    @Override

    public String getHeader(String name) {

    String header = super.getHeader(name);

if ("content-type".equalsIgnoreCase(name)){

System.out.println("Adds Header Content-Type as application/json");

return "application/json";

}

        return header;

    }

    

    @Override

    public Enumeration getHeaders(String name) {

        List values = Collections.list(super.getHeaders(name));

        if(name.equalsIgnoreCase("content-type")) {

            values.add("application/json");

        }

        return Collections.enumeration(values);

    }

    

    @Override

    public Enumeration getHeaderNames() {

        List names = Collections.list(super.getHeaderNames());

        names.addAll(Collections.list(super.getParameterNames()));

        String url = new String(((HttpServletRequest)super.getRequest()).getRequestURL());

if(!names.contains("content-type"))

names.add("content-type");

return Collections.enumeration(names);

    }

@Override

public String getParameter(String name) {

String paramValue = super.getParameter(name);

if (paramValue == null) {

paramValue = customHeaderMap.get(name);

}

return paramValue;

}