Generate oauth token

InternalAuthTokenGenerator.java

/*
 * Copyright 2016 Thitipong Jampajeen <jampajeen@gmail.com>.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.volho.smerp.web.service;

import com.volho.smerp.web.security.Authorities;
import java.security.Principal;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.authority.SimpleGrantedAuthority;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.oauth2.provider.endpoint.TokenEndpoint;
import org.springframework.stereotype.Component;
import org.springframework.web.HttpRequestMethodNotSupportedException;

/**
 *
 * @author Thitipong Jampajeen <jampajeen@gmail.com>
 * 
 * This class use TokenEndpoint object from spring context directly, it's not recommended.
 */
@Component
public class InternalAuthTokenGenerator {

    private static final Logger LOG = LoggerFactory.getLogger(InternalAuthTokenGenerator.class);

    @Autowired
    Config config;

    @Autowired
    private TokenEndpoint tokenEndpoint;

    public String authenticateAndGetToken() {

        try {
            Set<GrantedAuthority> authorities = new HashSet<GrantedAuthority>();
            authorities.add(new SimpleGrantedAuthority(Authorities.ROLE_USER.toString()));

            UsernamePasswordAuthenticationToken authentication = new UsernamePasswordAuthenticationToken(config.OAUTH_COMMON_REMOTE_CLIENTID, config.OAUTH_COMMON_REMOTE_SECRET, authorities);

            SecurityContextHolder.getContext().setAuthentication(authentication);
            Principal pl = (Principal) authentication;

            HashMap<String, String> parameters = new HashMap<String, String>();
            parameters.put("grant_type", "client_credentials");
            ResponseEntity obj = tokenEndpoint.getAccessToken(pl, parameters);
            return obj.getBody() + "";

        } catch (HttpRequestMethodNotSupportedException ex) {
            LOG.error("Cannot authenticate and generate token.");
        }
        return "";
    }
}