Merge pull request #18 from awslabs/servlet-improvements

Servlet filters support

Author: sapessi

README.md

@@ -141,3 +141,15 @@ public String echoServletHeaders(@Context HttpServletRequest context) {
     return "servlet";
 }
 ```
+
+## Servlet Filters
+You can register [`Filter`](https://docs.oracle.com/javaee/7/api/javax/servlet/Filter.html) implementations by implementing a `StartupsHandler` as defined in the `AwsLambdaServletContainerHandler` class. The `onStartup` methods receives a reference to the current `ServletContext`.
+
+```java
+handler.onStartup(c -> {
+    FilterRegistration.Dynamic registration = c.addFilter("CustomHeaderFilter", CustomHeaderFilter.class);
+    // update the registration to map to a path
+    registration.addMappingForUrlPatterns(EnumSet.of(DispatcherType.REQUEST), true, "/*");
+    // servlet name mappings are disabled and will throw an exception
+});
+```

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/LambdaContainerHandler.java

@@ -30,6 +30,12 @@
  */
 public abstract class LambdaContainerHandler<RequestType, ResponseType, ContainerRequestType, ContainerResponseType> {
 
+    //-------------------------------------------------------------
+    // Constants
+    //-------------------------------------------------------------
+
+    public static final String SERVER_INFO = "aws-serverless-java-container";
+
     //-------------------------------------------------------------
     // Variables - Private
     //-------------------------------------------------------------

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsFilterChainManager.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance
+ * with the License. A copy of the License is located at
+ *
+ * http://aws.amazon.com/apache2.0/
+ *
+ * or in the "license" file accompanying this file. This file 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.amazonaws.serverless.proxy.internal.servlet;
+
+import java.util.Map;
+
+/**
+ * This implementation of the <code>FilterChainManager</code> object uses the <code>AwsServletContext</code> object
+ * to extract a list of <code>FilterHolder</code>s
+ */
+public class AwsFilterChainManager extends FilterChainManager<AwsServletContext> {
+
+    //-------------------------------------------------------------
+    // Constructors
+    //-------------------------------------------------------------
+
+    /**
+     * Creates a new FilterChainManager for the given servlet context
+     * @param context An initialized AwsServletContext object
+     */
+    AwsFilterChainManager(AwsServletContext context) {
+        super(context);
+    }
+
+    //-------------------------------------------------------------
+    // Implementation - FilterChainManager
+    //-------------------------------------------------------------
+
+    /**
+     * Returns the filter holders stored in the <code>AwsServletContext</code> object
+     * @return The map of filter holders
+     */
+    protected Map<String, FilterHolder> getFilterHolders() {
+        return servletContext.getFilterHolders();
+    }
+}

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/servlet/AwsHttpServletRequest.java

@@ -0,0 +1,294 @@
+/*
+ * Copyright 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance
+ * with the License. A copy of the License is located at
+ *
+ * http://aws.amazon.com/apache2.0/
+ *
+ * or in the "license" file accompanying this file. This file 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.amazonaws.serverless.proxy.internal.servlet;
+
+import com.amazonaws.services.lambda.runtime.Context;
+
+import javax.servlet.AsyncContext;
+import javax.servlet.DispatcherType;
+import javax.servlet.ServletContext;
+import javax.servlet.http.Cookie;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpSession;
+import java.io.UnsupportedEncodingException;
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+import java.util.stream.Collectors;
+
+
+/**
+ * Base HttpServletRequest object. This object exposes some utility methods to work with request values such as headers
+ * and query string parameters. New implementations of <code>HttpServletRequest</code> can extend this class to reuse
+ * the utility methods
+ */
+public abstract class AwsHttpServletRequest implements HttpServletRequest {
+
+    //-------------------------------------------------------------
+    // Constants
+    //-------------------------------------------------------------
+
+    static final String HEADER_KEY_VALUE_SEPARATOR = "=";
+    static final String HEADER_VALUE_SEPARATOR = ";";
+    static final String FORM_DATA_SEPARATOR = "&";
+    static final String DEFAULT_CHARACTER_ENCODING = "UTF-8";
+    static final String HEADER_DATE_FORMAT = "EEE, d MMM yyyy HH:mm:ss z";
+    static final String ENCODING_VALUE_KEY = "charset";
+
+    // We need this to pickup the protocol from the CloudFront header since Lambda doesn't receive this
+    // information from anywhere else
+    static final String CF_PROTOCOL_HEADER_NAME = "CloudFront-Forwarded-Proto";
+
+
+    //-------------------------------------------------------------
+    // Variables - Private
+    //-------------------------------------------------------------
+
+    private Context lambdaContext;
+    private Map<String, Object> attributes;
+
+
+    //-------------------------------------------------------------
+    // Constructors
+    //-------------------------------------------------------------
+
+    /**
+     * Protected constructors for implemnenting classes. This should be called first with the context received from
+     * AWS Lambda
+     * @param lambdaContext The Lambda function context. This object is used for utility methods such as log
+     */
+    AwsHttpServletRequest(Context lambdaContext) {
+        this.lambdaContext = lambdaContext;
+        attributes = new HashMap<>();
+    }
+
+    //-------------------------------------------------------------
+    // Implementation - HttpServletRequest
+    //-------------------------------------------------------------
+
+    @Override
+    public String getRequestedSessionId() {
+        throw new UnsupportedOperationException();
+    }
+
+
+    @Override
+    public HttpSession getSession(boolean b) {
+        return null;
+    }
+
+
+    @Override
+    public HttpSession getSession() {
+        return null;
+    }
+
+
+    @Override
+    public String changeSessionId() {
+        return null;
+    }
+
+
+    @Override
+    public boolean isRequestedSessionIdValid() {
+        return false;
+    }
+
+
+    @Override
+    public boolean isRequestedSessionIdFromCookie() {
+        return false;
+    }
+
+
+    @Override
+    public boolean isRequestedSessionIdFromURL() {
+        return false;
+    }
+
+
+    @Override
+    public boolean isRequestedSessionIdFromUrl() {
+        return false;
+    }
+
+
+    //-------------------------------------------------------------
+    // Implementation - ServletRequest
+    //-------------------------------------------------------------
+
+
+    @Override
+    public Object getAttribute(String s) {
+        return attributes.get(s);
+    }
+
+
+    @Override
+    public Enumeration<String> getAttributeNames() {
+        return Collections.enumeration(attributes.keySet());
+    }
+
+
+    @Override
+    public String getServerName() {
+        return "lambda.amazonaws.com";
+    }
+
+
+    @Override
+    public int getServerPort() {
+        return 0;
+    }
+
+
+    @Override
+    public void setAttribute(String s, Object o) {
+        attributes.put(s, o);
+    }
+
+
+    @Override
+    public void removeAttribute(String s) {
+        attributes.remove(s);
+    }
+
+
+    @Override
+    public String getLocalName() {
+        return "lambda.amazonaws.com";
+    }
+
+
+    @Override
+    public String getLocalAddr() {
+        return null;
+    }
+
+
+    @Override
+    public int getLocalPort() {
+        return 0;
+    }
+
+
+    @Override
+    public ServletContext getServletContext() {
+        return AwsServletContext.getInstance(lambdaContext);
+    }
+
+
+    @Override
+    public boolean isAsyncStarted() {
+        return false;
+    }
+
+
+    @Override
+    public boolean isAsyncSupported() {
+        return false;
+    }
+
+
+    @Override
+    public AsyncContext getAsyncContext() {
+        return null;
+    }
+
+
+    @Override
+    public DispatcherType getDispatcherType() {
+        return DispatcherType.REQUEST;
+    }
+
+
+    //-------------------------------------------------------------
+    // Methods - Protected
+    //-------------------------------------------------------------
+
+    /**
+     * Given the Cookie header value, parses it and creates a Cookie object
+     * @param headerValue The string value of the HTTP Cookie header
+     * @return An array of Cookie objects from the header
+     */
+    protected Cookie[] parseCookieHeaderValue(String headerValue) {
+
+        List<Map.Entry<String, String>> parsedHeaders = this.parseHeaderValue(headerValue);
+
+        return parsedHeaders.stream()
+                            .filter(e -> e.getKey() != null)
+                            .map(e -> new Cookie(e.getKey(), e.getValue()))
+                            .toArray(Cookie[]::new);
+    }
+
+    /**
+     * Given a map of key/values query string parameters from API Gateway, creates a query string as it would have
+     * been in the original url.
+     * @param parameters A Map<String, String> of query string parameters
+     * @return The generated query string for the URI
+     */
+    protected String generateQueryString(Map<String, String> parameters) {
+        if (parameters == null || parameters.size() == 0) {
+            return null;
+        }
+
+        return parameters.keySet().stream()
+                .map(key -> {
+                    String newKey = key;
+                    String newValue = parameters.get(key);
+                    try {
+                        if (!URLEncoder.encode(newKey, StandardCharsets.UTF_8.name()).equals(newKey)) {
+                            newKey = URLEncoder.encode(key, StandardCharsets.UTF_8.name());
+                        }
+
+                        if (!URLEncoder.encode(newValue, StandardCharsets.UTF_8.name()).equals(newValue)) {
+                            newValue = URLEncoder.encode(newValue, StandardCharsets.UTF_8.name());
+                        }
+                    } catch (UnsupportedEncodingException e) {
+                        lambdaContext.getLogger().log("Could not URLEncode: " + newKey + "\n" + e.getLocalizedMessage());
+                        e.printStackTrace();
+
+                    }
+                    return newKey + "=" + newValue;
+                })
+                .collect(Collectors.joining("&"));
+    }
+
+
+    /**
+     * Generic method to parse an HTTP header value and split it into a list of key/values for all its components.
+     * When the property in the header does not specify a key the key field in the output pair is null and only the value
+     * is populated. For example, The header <code>Accept: application/json; application/xml</code> will contain two
+     * key value pairs with key null and the value set to application/json and application/xml respectively.
+     *
+     * @param headerValue The string value for the HTTP header
+     * @return A list of SimpleMapEntry objects with all of the possible values for the header.
+     */
+    protected List<Map.Entry<String, String>> parseHeaderValue(String headerValue) {
+        List<Map.Entry<String, String>> values = new ArrayList<>();
+        if (headerValue == null) {
+            return values;
+        }
+        for (String kv : headerValue.split(HEADER_VALUE_SEPARATOR)) {
+            String[] kvSplit = kv.split(HEADER_KEY_VALUE_SEPARATOR);
+
+            if (kvSplit.length != 2) {
+                values.add(new AbstractMap.SimpleEntry<>(null, kv.trim()));
+            } else {
+                values.add(new AbstractMap.SimpleEntry<>(kvSplit[0].trim(), kvSplit[1].trim()));
+            }
+        }
+        return values;
+    }
+}