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Instrumentation for the Servlet API
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/*
 * Copyright 2011-2019 the original author or authors.
 *
 * 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 org.glowroot.instrumentation.servlet;

import java.util.List;
import java.util.Map;

import org.glowroot.instrumentation.api.ThreadContext;
import org.glowroot.instrumentation.api.ThreadContext.Priority;
import org.glowroot.instrumentation.api.checker.Nullable;
import org.glowroot.instrumentation.api.util.Beans;
import org.glowroot.instrumentation.api.weaving.Advice;
import org.glowroot.instrumentation.api.weaving.Bind;
import org.glowroot.instrumentation.servlet.boot.ServletInstrumentationProperties;
import org.glowroot.instrumentation.servlet.boot.ServletInstrumentationProperties.SessionAttributePath;
import org.glowroot.instrumentation.servlet.boot.ServletMessageSupplier;
import org.glowroot.instrumentation.servlet.boot.Strings;

public class SessionInstrumentation {

    @Advice.Pointcut(className = "javax.servlet.http.HttpSession",
                     methodName = "setAttribute|putValue",
                     methodParameterTypes = {"java.lang.String", "java.lang.Object"},
                     nestingGroup = "servlet-inner-call")
    public static class SetAttributeAdvice {

        @Advice.OnMethodAfter
        public static void onAfter(
                @Bind.Argument(0) @Nullable String name,
                @Bind.Argument(1) @Nullable Object value,
                ThreadContext context) {

            onAfterCommon(name, value, context);
        }
    }

    @Advice.Pointcut(className = "javax.servlet.http.HttpSession",
                     methodName = "removeAttribute",
                     methodParameterTypes = {"java.lang.String"},
                     nestingGroup = "servlet-inner-call")
    public static class RemoveAttributeAdvice {

        @Advice.OnMethodAfter
        public static void onAfter(
                @Bind.Argument(0) @Nullable String name,
                ThreadContext context) {

            // calling HttpSession.setAttribute() with null value is the same as calling
            // removeAttribute(), per the setAttribute() javadoc
            onAfterCommon(name, null, context);
        }
    }

    private static void onAfterCommon(@Nullable String name, @Nullable Object value,
            ThreadContext context) {

        if (name == null) {
            // theoretically possible, so just ignore
            return;
        }
        // name is non-null per HttpSession.setAttribute() javadoc, but value may be null
        // (which per the javadoc is the same as calling removeAttribute())
        ServletMessageSupplier messageSupplier =
                (ServletMessageSupplier) context.getServletRequestInfo();
        if (messageSupplier != null) {
            updateUserIfApplicable(name, value, context);
            updateSessionAttributesIfApplicable(messageSupplier, name, value);
        }
    }

    private static void updateUserIfApplicable(String attributeName,
            @Nullable Object attributeValue,
            ThreadContext context) {

        if (attributeValue == null) {
            // if user value is set to null, don't clear it
            return;
        }
        SessionAttributePath userAttributePath =
                ServletInstrumentationProperties.userAttributePath();
        if (userAttributePath == null) {
            return;
        }
        if (!userAttributePath.getAttributeName().equals(attributeName)) {
            return;
        }
        // capture user now, don't use a lazy supplier
        List nestedPath = userAttributePath.getNestedPath();
        if (nestedPath.isEmpty()) {
            context.setTransactionUser(attributeValue.toString(),
                    Priority.CORE_INSTRUMENTATION);
        } else {
            Object user;
            try {
                user = Beans.value(attributeValue, nestedPath);
            } catch (Exception e) {
                user = "";
            }
            if (user != null) {
                // if user is null, don't clear it
                context.setTransactionUser(user.toString(), Priority.CORE_INSTRUMENTATION);
            }
        }
    }

    private static void updateSessionAttributesIfApplicable(
            ServletMessageSupplier messageSupplier, String attributeName,
            @Nullable Object attributeValue) {

        if (ServletInstrumentationProperties.captureSessionAttributeNames()
                .contains(attributeName)
                || ServletInstrumentationProperties.captureSessionAttributeNames()
                        .contains("*")) {
            // update all session attributes (possibly nested) at or under the set attribute
            for (SessionAttributePath attributePath : ServletInstrumentationProperties
                    .captureSessionAttributePaths()) {
                if (attributePath.getAttributeName().equals(attributeName)
                        || attributePath.isAttributeNameWildcard()) {
                    if (attributePath.getNestedPath().isEmpty()
                            && !attributePath.isWildcard()) {
                        updateSessionAttribute(messageSupplier, attributeName, attributeValue);
                    } else {
                        updateNestedSessionAttributes(messageSupplier, attributePath,
                                attributeValue);
                    }
                }
            }
        }
    }

    private static void updateSessionAttribute(ServletMessageSupplier messageSupplier,
            String attributeName, @Nullable Object attributeValue) {

        if (attributeValue == null) {
            messageSupplier.putSessionAttributeChangedValue(attributeName, null);
        } else {
            messageSupplier.putSessionAttributeChangedValue(attributeName,
                    Strings.nullToEmpty(attributeValue.toString()));
        }
    }

    private static void updateNestedSessionAttributes(ServletMessageSupplier messageSupplier,
            SessionAttributePath attributePath, @Nullable Object attributeValue) {

        String fullPath = attributePath.getFullPath();
        if (attributePath.isWildcard()) {
            Object val = HttpSessions.getSessionAttribute(attributeValue, attributePath);
            if (val == null) {
                messageSupplier.putSessionAttributeChangedValue(fullPath, null);
            } else if (val instanceof Map) {
                for (Map.Entry entry : ((Map) val).entrySet()) {
                    Object v = entry.getValue();
                    messageSupplier.putSessionAttributeChangedValue(
                            fullPath + "." + entry.getKey(),
                            v == null ? null : Strings.nullToEmpty(v.toString()));
                }
            } else {
                for (Map.Entry entry : Beans.propertiesAsText(val).entrySet()) {
                    messageSupplier.putSessionAttributeChangedValue(
                            fullPath + "." + entry.getKey(), entry.getValue());
                }
            }
        } else if (attributeValue == null) {
            // no need to navigate path since it will always be null
            messageSupplier.putSessionAttributeChangedValue(fullPath, null);
        } else {
            Object val = HttpSessions.getSessionAttribute(attributeValue, attributePath);
            messageSupplier.putSessionAttributeChangedValue(fullPath,
                    val == null ? null : Strings.nullToEmpty(val.toString()));
        }
    }
}