This sample demonstrates how to use the [Logs API][appid] on [Google App

Engine][ae-docs].

[appid]: https://cloud.google.com/appengine/docs/java/logs/

[ae-docs]: https://cloud.google.com/appengine/docs/java/

The Logs API only generates output for deployed apps, so this program should not be run locally.

This example uses the

[Maven gcloud plugin](https://cloud.google.com/appengine/docs/java/managed-vms/maven).

In the following command, replace YOUR-PROJECT-ID with your

[Google Cloud Project ID](https://developers.google.com/console/help/new/#projectnumber).

In the following command, replace YOUR-PROJECT-ID with your

[Google Cloud Project ID](https://developers.google.com/console/help/new/#projectnumber) and SOME-VERSION with the desired version number.

$ mvn appengine:update -Dappengine.appId=YOUR-PROJECT-ID -Dappengine.version=SOME-VERSION

To save your project settings so that you don't need to enter the

parameters, you can:

1. Update the <application> tag in src/main/webapp/WEB-INF/appengine-web.xml

with your project name.

2. Update the <version> tag in src/main/webapp/WEB-INF/appengine-web.xml

with a valid version number.

You will now be able to run

$ mvn appengine:update

without the need for any additional parameters.

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

<modelVersion>4.0.0</modelVersion>

<packaging>war</packaging>

<version>1.0-SNAPSHOT</version>

<groupId>com.example.appengine</groupId>

<artifactId>appengine-logs</artifactId>

<!-- Parent POM defines ${appengine.sdk.version} (updates frequently). -->

<parent>

<groupId>com.google.cloud</groupId>

<artifactId>doc-samples</artifactId>

<version>1.0.0</version>

<relativePath>../..</relativePath>

</parent>

<dependencies>

<dependency>

<groupId>com.google.appengine</groupId>

<artifactId>appengine-api-1.0-sdk</artifactId>

<version>${appengine.sdk.version}</version>

</dependency>

<dependency>

<groupId>com.google.guava</groupId>

<artifactId>guava</artifactId>

<version>19.0</version>

</dependency>

<dependency>

<groupId>javax.servlet</groupId>

<artifactId>servlet-api</artifactId>

<version>2.5</version>

<type>jar</type>

<scope>provided</scope>

</dependency>

<dependency>

<groupId>org.json</groupId>

<artifactId>json</artifactId>

<version>20151123</version>

</dependency>

</dependencies>

<build>

<!-- for hot reload of the web application -->

<outputDirectory>${project.build.directory}/${project.build.finalName}/WEB-INF/classes</outputDirectory>

<plugins>

<plugin>

<groupId>org.apache.maven.plugins</groupId>

<version>3.3</version>

<artifactId>maven-compiler-plugin</artifactId>

<configuration>

<source>1.7</source>

<target>1.7</target>

</configuration>

</plugin>

<plugin>

<groupId>com.google.appengine</groupId>

<artifactId>appengine-maven-plugin</artifactId>

<version>${appengine.sdk.version}</version>

</plugin>

</plugins>

</build>

</project>

package com.example.appengine.logs;

import com.google.appengine.api.log.AppLogLine;

import com.google.appengine.api.log.LogQuery;

import com.google.appengine.api.log.LogServiceFactory;

import com.google.appengine.api.log.RequestLogs;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Calendar;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class LogsServlet extends HttpServlet {

@Override

public void doGet(HttpServletRequest req, HttpServletResponse resp)

throws IOException {

resp.setContentType("text/html");

PrintWriter writer = resp.getWriter();

// We use this to break out of our iteration loop, limiting record

// display to 5 request logs at a time.

int limit = 5;

// This retrieves the offset from the Next link upon user click.

String offset = req.getParameter("offset");

// We want the App logs for each request log

LogQuery query = LogQuery.Builder.withDefaults();

query.includeAppLogs(true);

// Set the offset value retrieved from the Next link click.

if (offset != null) {

query.offset(offset);

}

// This gets filled from the last request log in the iteration

String lastOffset = null;

int count = 0;

// Display a few properties of each request log.

for (RequestLogs record : LogServiceFactory.getLogService().fetch(query)) {

writer.println("<br />REQUEST LOG <br />");

Calendar cal = Calendar.getInstance();

cal.setTimeInMillis(record.getStartTimeUsec() / 1000);

writer.println("IP: " + record.getIp() + "<br />");

writer.println("Method: " + record.getMethod() + "<br />");

writer.println("Resource " + record.getResource() + "<br />");

writer.println(String.format("<br />Date: %s", cal.getTime().toString()));

lastOffset = record.getOffset();

// Display all the app logs for each request log.

for (AppLogLine appLog : record.getAppLogLines()) {

writer.println("<br />" + "APPLICATION LOG" + "<br />");

Calendar appCal = Calendar.getInstance();

appCal.setTimeInMillis(appLog.getTimeUsec() / 1000);

writer.println(String.format("<br />Date: %s",

appCal.getTime().toString()));

writer.println("<br />Level: " + appLog.getLogLevel() + "<br />");

writer.println("Message: " + appLog.getLogMessage() + "<br /> <br />");

} //for each log line

if (++count >= limit) {

break;

}

} // for each record

// When the user clicks this link, the offset is processed in the

// GET handler and used to cycle through to the next 5 request logs.

writer.println(String.format("<br><a href=\"/?offset=%s\">Next</a>",

lastOffset));

} // end doGet

} //end class

<?xml version="1.0" encoding="utf-8"?>

<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">

<application>YOUR-PROJECT-ID</application>

<version>YOUR-VERSION-NUMBER</version>

<threadsafe>true</threadsafe>

<system-properties>

<property name="java.util.logging.config.file" value="WEB-INF/logging.properties"/>

</system-properties>

</appengine-web-app>

.level = WARNING

<?xml version="1.0" encoding="utf-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee"

xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"

xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"

version="2.5">

<servlet>

<servlet-name>logs</servlet-name>

<servlet-class>com.example.appengine.logs.LogsServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>logs</servlet-name>

<url-pattern>/</url-pattern>

</servlet-mapping>

</web-app>

<module>appengine/logs</module>