I am studying Spring OAuth by decomposing this set of three interconnected apps at GitHub, while also carefully studying the Spring OAuth 2 Developer Guide at this link. The Developer Guide says that the /oauth/error endpoint needs to be customized, but what specific code should be use to accomplish a successful override of /oauth/error?
FIRST ATTEMPT:
My first attempt at doing the override, is throwing errors, which you can see in the debug log, which I have uploaded to a file sharing site at this link.
I started by trying to get code elements provided by Spring to work in the sample app.
First, I added a new controller class to the authserver app in the sample app link above, and I added some of the sample code from Spring's WhiteLabelErrorEndpoint.java, which you can read at this link. My attempt is as follows:
package demo;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.springframework.security.oauth2.common.exceptions.OAuth2Exception;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.util.HtmlUtils;
@Controller
public class CustomViewsController {
private static final String ERROR = "<html><body><h1>OAuth Error</h1><p>${errorSummary}</p></body></html>";
@RequestMapping("/oauth/error")
public ModelAndView handleError(HttpServletRequest request) {
Map<String, Object> model = new HashMap<String, Object>();
Object error = request.getAttribute("error");
// The error summary may contain malicious user input,
// it needs to be escaped to prevent XSS
String errorSummary;
if (error instanceof OAuth2Exception) {
OAuth2Exception oauthError = (OAuth2Exception) error;
errorSummary = HtmlUtils.htmlEscape(oauthError.getSummary());
}
else {
errorSummary = "Unknown error";
}
model.put("errorSummary", errorSummary);
return new ModelAndView(new SpelView(ERROR), model);
}
}
And I added the following SpelView.java String handler class used by the link above by copying the code from this link:
package demo;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.context.expression.MapAccessor;
import org.springframework.expression.Expression;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.security.oauth2.common.util.RandomValueStringGenerator;
import org.springframework.util.PropertyPlaceholderHelper;
import org.springframework.util.PropertyPlaceholderHelper.PlaceholderResolver;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
/**
* Simple String template renderer.
*
*/
class SpelView implements View {
private final String template;
private final String prefix;
private final SpelExpressionParser parser = new SpelExpressionParser();
private final StandardEvaluationContext context = new StandardEvaluationContext();
private PlaceholderResolver resolver;
public SpelView(String template) {
this.template = template;
this.prefix = new RandomValueStringGenerator().generate() + "{";
this.context.addPropertyAccessor(new MapAccessor());
this.resolver = new PlaceholderResolver() {
public String resolvePlaceholder(String name) {
Expression expression = parser.parseExpression(name);
Object value = expression.getValue(context);
return value == null ? null : value.toString();
}
};
}
public String getContentType() {
return "text/html";
}
public void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response)
throws Exception {
Map<String, Object> map = new HashMap<String, Object>(model);
String path = ServletUriComponentsBuilder.fromContextPath(request).build()
.getPath();
map.put("path", (Object) path==null ? "" : path);
context.setRootObject(map);
String maskedTemplate = template.replace("${", prefix);
PropertyPlaceholderHelper helper = new PropertyPlaceholderHelper(prefix, "}");
String result = helper.replacePlaceholders(maskedTemplate, resolver);
result = result.replace(prefix, "${");
response.setContentType(getContentType());
response.getWriter().append(result);
}
}
