Packages 
Package Description
org.apache.catalina  
org.apache.catalina.ant
This package contains a set of Task implementations for Ant (version 1.6.x or later) that can be used to interact with the Manager application to deploy, undeploy, list, reload, start and stop web applications from a running instance of Tomcat.
org.apache.catalina.ant.jmx
This package contains a set of JMX Task implementations for Ant (version 1.6 or later) that can be used to interact with the Remote JMX JSR 160 RMI Adaptor to get/set attributes, invoke MBean operations and query for Mbeans inside a running instance of Tomcat.
org.apache.catalina.authenticator
This package contains Authenticator implementations for the various supported authentication methods (BASIC, DIGEST, and FORM).
org.apache.catalina.authenticator.jaspic  
org.apache.catalina.connector  
org.apache.catalina.core  
org.apache.catalina.deploy  
org.apache.catalina.filters  
org.apache.catalina.ha
This package contains code for Clustering, the base class of a Cluster is org.apache.catalina.Cluster implementations of this class is done when implementing a new Cluster protocol
org.apache.catalina.ha.authenticator  
org.apache.catalina.ha.backend  
org.apache.catalina.ha.context  
org.apache.catalina.ha.deploy  
org.apache.catalina.ha.session  
org.apache.catalina.ha.tcp  
org.apache.catalina.loader  
org.apache.catalina.manager  
org.apache.catalina.manager.host  
org.apache.catalina.manager.util  
org.apache.catalina.mapper  
org.apache.catalina.mbeans  
org.apache.catalina.realm
This package contains Realm implementations for the various supported realm technologies for authenticating users and identifying their associated roles.
org.apache.catalina.security  
org.apache.catalina.servlets
This package contains Servlets that implement some of the standard functionality provided by the Catalina servlet container.
org.apache.catalina.session
This package contains the standard Manager and Session implementations that represent the collection of active sessions and the individual sessions themselves, respectively, that are associated with a Context.
org.apache.catalina.ssi
This package contains code that is used by the SsiInvoker.
org.apache.catalina.startup  
org.apache.catalina.storeconfig  
org.apache.catalina.tribes
QuickStart
org.apache.catalina.tribes.group  
org.apache.catalina.tribes.group.interceptors  
org.apache.catalina.tribes.io  
org.apache.catalina.tribes.jmx  
org.apache.catalina.tribes.membership  
org.apache.catalina.tribes.membership.cloud  
org.apache.catalina.tribes.tipis  
org.apache.catalina.tribes.transport  
org.apache.catalina.tribes.transport.nio  
org.apache.catalina.tribes.util  
org.apache.catalina.users  
org.apache.catalina.util  
org.apache.catalina.valves
This package contains a variety of small Valve implementations that do not warrant being packaged separately.
org.apache.catalina.valves.rewrite  
org.apache.catalina.webresources  
org.apache.catalina.webresources.war  
org.apache.coyote  
org.apache.coyote.ajp  
org.apache.coyote.http11  
org.apache.coyote.http11.filters  
org.apache.coyote.http11.upgrade  
org.apache.coyote.http2  
org.apache.el  
org.apache.el.lang  
org.apache.el.stream  
org.apache.el.util  
org.apache.jasper  
org.apache.jasper.compiler  
org.apache.jasper.compiler.tagplugin  
org.apache.jasper.el  
org.apache.jasper.optimizations  
org.apache.jasper.runtime  
org.apache.jasper.security  
org.apache.jasper.servlet  
org.apache.jasper.tagplugins.jstl  
org.apache.jasper.tagplugins.jstl.core  
org.apache.jasper.util  
org.apache.juli  
org.apache.juli.logging
Overview
org.apache.naming
This package contains a memory based naming service provider.
org.apache.naming.factory
This package contains object factories used by the naming service.
org.apache.naming.factory.webservices  
org.apache.naming.java
This package contains the URL context factory for the "java" namespace.
org.apache.tomcat  
org.apache.tomcat.buildutil  
org.apache.tomcat.buildutil.translate  
org.apache.tomcat.dbcp.dbcp2
Database Connection Pool API.
org.apache.tomcat.dbcp.dbcp2.cpdsadapter
This package contains one public class which is a ConnectionPoolDataSource (CPDS) implementation that can be used to adapt older Driver based JDBC implementations.
org.apache.tomcat.dbcp.dbcp2.datasources
This package contains two DataSources: PerUserPoolDataSource and SharedPoolDataSource which provide a database connection pool.
org.apache.tomcat.dbcp.dbcp2.managed
This package provides support for pooling of ManagedConnections.
org.apache.tomcat.dbcp.pool2
Object pooling API.
org.apache.tomcat.dbcp.pool2.impl
Object pooling API implementations.
org.apache.tomcat.jdbc.naming  
org.apache.tomcat.jdbc.pool  
org.apache.tomcat.jdbc.pool.interceptor  
org.apache.tomcat.jdbc.pool.jmx  
org.apache.tomcat.jni  
org.apache.tomcat.util  
org.apache.tomcat.util.bcel
This package contains basic classes for the Byte Code Engineering Library and constants defined by the JVM specification.
org.apache.tomcat.util.bcel.classfile
This package contains the classes that describe the structure of a Java class file and a class file parser.
org.apache.tomcat.util.buf
Buffers and Encodings
org.apache.tomcat.util.codec.binary
Base64, Base32, Binary, and Hexadecimal String encoding and decoding.
org.apache.tomcat.util.collections  
org.apache.tomcat.util.compat  
org.apache.tomcat.util.descriptor  
org.apache.tomcat.util.descriptor.tagplugin  
org.apache.tomcat.util.descriptor.tld
Package containing a Java model of the XML for a Tag Library Descriptor.
org.apache.tomcat.util.descriptor.web
This package contains Java objects that represent complex data structures from the web application deployment descriptor file (web.xml).
org.apache.tomcat.util.digester
The Digester package provides for rules-based processing of arbitrary XML documents.
org.apache.tomcat.util.file
This package contains utility classes for file handling.
org.apache.tomcat.util.http
Special utils for handling HTTP-specific entities - headers, parameters, cookies, etc.
org.apache.tomcat.util.http.fileupload
NOTE: This code has been copied from commons-fileupload trunk 1.3 and commons-io 1.4 and package renamed to avoid clashes with any web apps that may wish to use these libraries.
org.apache.tomcat.util.http.fileupload.disk
A disk-based implementation of the FileItem interface.
org.apache.tomcat.util.http.fileupload.impl
Implementations and exceptions utils.
org.apache.tomcat.util.http.fileupload.servlet
An implementation of FileUpload for use in servlets conforming to JSR 53.
org.apache.tomcat.util.http.fileupload.util
This package contains various IO related utility classes or methods, which are basically reusable and not necessarily restricted to the scope of a file upload.
org.apache.tomcat.util.http.fileupload.util.mime
MIME decoder implementation, imported and retailed from Apache Geronimo.
org.apache.tomcat.util.http.parser  
org.apache.tomcat.util.log  
org.apache.tomcat.util.modeler
The Modeler component of the Commons project offers convenient support for configuring and instantiating Model MBeans (management beans), as described in the JMX Specification.
org.apache.tomcat.util.modeler.modules
Implementation classes - should not be used directly.
org.apache.tomcat.util.net  
org.apache.tomcat.util.net.jsse  
org.apache.tomcat.util.net.openssl  
org.apache.tomcat.util.net.openssl.ciphers  
org.apache.tomcat.util.res  
org.apache.tomcat.util.scan
This package contains the common classes used to perform configuration scanning for Catalina and Jasper.
org.apache.tomcat.util.security  
org.apache.tomcat.util.threads  
org.apache.tomcat.util.xreflection  
org.apache.tomcat.websocket  
org.apache.tomcat.websocket.pojo
This package provides the necessary plumbing to convert an annotated POJO into a WebSocket Endpoint.
org.apache.tomcat.websocket.server
Server-side specific implementation classes.