## System Properties

### Table of Contents

- Introduction
- Property replacements
- Clustering
- Expression Language
- Jasper
- Security
- Specifications
- Sessions
- Logging
- JAR Scanning
- Websockets
- Other

### Introduction

The following sections list the system properties that may be set to modify the default Tomcat behaviour.

### Property replacements

Property | Description
--- | ---
`org.apache.tomcat.util.digester. PROPERTY_SOURCE` | Set this to a comma separated list of fully qualified name of classes that implement `org.apache.tomcat.util.IntrospectionUtils.PropertySource`. Required to have a public constructor with no arguments. Use this to add a property source, that will be invoked when `${parameter:default-value}` denoted parameters (with optional default values) are found in the XML files that Tomcat parses. Property replacement from the specified property source on the JVM system properties can also be done using the `REPLACE_SYSTEM_PROPERTIES` system property. `org.apache.tomcat.util.digester.EnvironmentPropertySource` can be used to replace parameters from the process' environment variables, e.g. injected ConfigMaps or Secret objects in container based systems like OpenShift or Kubernetes.
`org.apache.tomcat.util.digester. REPLACE_SYSTEM_PROPERTIES` | Set this boolean system property to `true` to cause property replacement from the digester property source on the JVM system properties.

### Clustering

Property | Description
--- | ---
`org.apache.catalina. tribes.dns_lookups` | This system property is deprecated and will be removed without replacement in Apache Tomcat 10 onwards. If `true`, the clustering module will attempt to use DNS to resolve any host names provided in the cluster configuration. If not specified, the default value of `false` will be used.

### Expression Language

Property | Description
--- | ---
`org.apache.el.BeanELResolver. CACHE_SIZE` | The number of javax.el.BeanELResolver.BeanProperties objects that will be cached by the EL Parser. If not specified, the default of `1000` will be used.
`org.apache.el.ExpressionBuilder. CACHE_SIZE` | The number of parsed EL expressions that will be cached by the EL Parser. If not specified, the default of `5000` will be used.
`org.apache.el.parser. COERCE_TO_ZERO` | If `true`, when coercing `null`s to objects of type Number, Character or Boolean the result will be `0` for Number and Character types and `false` for Boolean as required by the EL 2.2 and earlier specifications. If this property is `false` the result of the coercion will be `null` as required by the EL 3.0 specification. If not specified, the default value of `false` will be used.
`org.apache.el.parser. SKIP_IDENTIFIER_CHECK` | If `true`, when parsing expressions, identifiers will not be checked to ensure that they conform to the Java Language Specification for Java identifiers. If not specified, the default value of `false` will be used.

### Jasper

Property | Description
--- | ---
`org.apache.jasper.compiler. Generator.POOL_TAGS_WITH_EXTENDS` | By default, JSPs that use their own base class via the extends attribute of the page directive, will have Tag pooling disabled since Jasper cannot guarantee that the necessary initialisation will have taken place. This can have a negative impact on performance. Providing the alternative base class calls _jspInit() from Servlet.init(), setting this property to `true` will enable pooling with an alternative base class. If the alternative base class does not call _jspInit() and this property is `true`, NPEs will occur when attempting to use tags. If not specified, the default value of `false` will be used.
`org.apache.jasper.compiler. Generator.STRICT_GET_PROPERTY` | If `true`, the requirement to have the object referenced in `jsp:getProperty` action to be previously "introduced" to the JSP processor, as specified in the chapter JSP.5.3 of JSP 2.0 and later specifications, is enforced. If not specified, the specification compliant default of `true` will be used.
`org.apache.jasper.compiler. Generator.VAR_EXPRESSIONFACTORY` | The name of the variable to use for the expression language expression factory. If not specified, the default value of `_el_expressionfactory` will be used.
`org.apache.jasper.compiler. Generator.VAR_INSTANCEMANAGER` | The name of the variable to use for the instance manager factory. If not specified, the default value of `_jsp_instancemanager` will be used.
`org.apache.jasper.compiler. Parser.STRICT_WHITESPACE` | If `false` the requirements for whitespace before an attribute name will be relaxed so that the lack of whitespace will not cause an error. If not specified, the specification compliant default of `true` will be used.
`org.apache.jasper.runtime. BodyContentImpl.BUFFER_SIZE` | The size (in characters) to use when creating a tag buffer. If not specified, the default value of `org.apache.jasper.Constants.DEFAULT_TAG_BUFFER_SIZE` (512) will be used.
`org.apache.jasper.runtime. BodyContentImpl.LIMIT_BUFFER` | If `true`, any tag buffer that expands beyond `org.apache.jasper.runtime.BodyContentImpl.BUFFER_SIZE` will be destroyed and a new buffer created. If not specified, the default value of `false` will be used.
`org.apache.jasper.runtime. JspFactoryImpl.USE_POOL` | If `true`, a ThreadLocal `PageContext` pool will be used. If not specified, the default value of `true` will be used.
`org.apache.jasper.runtime. JspFactoryImpl.POOL_SIZE` | The size of the ThreadLocal `PageContext`. If not specified, the default value of `8` will be used.
`org.apache.jasper.Constants. JSP_SERVLET_BASE` | The base class of the Servlets generated from the JSPs. If not specified, the default value of `org.apache.jasper.runtime.HttpJspBase` will be used.
`org.apache.jasper.Constants. SERVICE_METHOD_NAME` | The name of the service method called by the base class. If not specified, the default value of `_jspService` will be used.
`org.apache.jasper.Constants. SERVLET_CLASSPATH` | The name of the ServletContext attribute that provides the classpath for the JSP. If not specified, the default value of `org.apache.catalina.jsp_classpath` will be used.
`org.apache.jasper.Constants. JSP_FILE` | The name of the request attribute for `<jsp-file>` element of a servlet definition. If present on a request, this overrides the value returned by `request.getServletPath()` to select the JSP page to be executed. If not specified, the default value of `org.apache.catalina.jsp_file` will be used. Deprecated: This will be removed in Tomcat 9.0.x onwards. It is replaced by the use of the jspFile servlet initialisation parameter
`org.apache.jasper.Constants. PRECOMPILE` | The name of the query parameter that causes the JSP engine to just pregenerate the servlet but not invoke it. If not specified, the default value of `jsp_precompile` will be used, as defined by JSP specification (JSP.11.4.2).
`org.apache.jasper.Constants. JSP_PACKAGE_NAME` | The default package name for compiled JSPs. If not specified, the default value of `org.apache.jsp` will be used.
`org.apache.jasper.Constants. TAG_FILE_PACKAGE_NAME` | The default package name for tag handlers generated from tag files. If not specified, the default value of `org.apache.jsp.tag` will be used.
`org.apache.jasper.Constants. ALT_DD_ATTR` | The servlet context attribute under which the alternate deployment descriptor for this web application is stored. If not specified, the default value of `org.apache.catalina.deploy.alt_dd` will be used.
`org.apache.jasper.Constants. TEMP_VARIABLE_NAME_PREFIX` | Prefix to use for generated temporary variable names. If not specified, the default value of `_jspx_temp` will be used.
`org.apache.jasper.Constants. USE_INSTANCE_MANAGER_FOR_TAGS` | If `true`, the instance manager is used to obtain tag handler instances. If not specified, the default value of `false` will be used.

### Security

Property | Description
--- | ---
`org.apache.catalina.connector. RECYCLE_FACADES` | If this is `true` or if a security manager is in use a new facade object will be created for each request. If not specified, the default value of `false` will be used.
`org.apache.catalina.connector. CoyoteAdapter.ALLOW_BACKSLASH` | If this is `true` the '\' character will be permitted as a path delimiter. If not specified, the default value of `false` will be used.
`org.apache.tomcat.util.buf. UDecoder.ALLOW_ENCODED_SLASH` | Use of this system property is deprecated. It will be removed from Tomcat 10 onwards. If this system property is set to `true`, the default for the `encodedSolidusHandling` attribute of all Connectors will be changed from `reject` to `decode`. If decoded, it will be treated a path delimiter.

### Specifications

Property | Description
--- | ---
`org.apache.catalina. STRICT_SERVLET_COMPLIANCE` | The default value of this system property is `false`. If this is `true` the default values will be changed for: `org.apache.catalina.core. ApplicationContext.GET_RESOURCE_REQUIRE_SLASH` `org.apache.catalina.core. ApplicationDispatcher.WRAP_SAME_OBJECT` `org.apache.catalina.core. StandardHostValve.ACCESS_SESSION` `org.apache.catalina.session. StandardSession.ACTIVITY_CHECK` `org.apache.catalina.session. StandardSession.LAST_ACCESS_AT_START` `org.apache.tomcat.util.http. ServerCookie.STRICT_NAMING` The `resourceOnlyServlets` attribute of any Context element. The `tldValidation` attribute of any Context element. The `useRelativeRedirects` attribute of any Context element. The `xmlNamespaceAware` attribute of any Context element. The `xmlValidation` attribute of any Context element.
`org.apache.catalina.connector. Response.ENFORCE_ENCODING_IN_GET_WRITER` | If this is `true` then a call to `Response.getWriter()` if no character encoding has been specified will result in subsequent calls to `Response.getCharacterEncoding()` returning `ISO-8859-1` and the `Content-Type` response header will include a `charset=ISO-8859-1` component. (SRV.15.2.22.1) If not specified, the default specification compliant value of `true` will be used.
`org.apache.catalina.core.ApplicationContext .GET_RESOURCE_REQUIRE_SLASH` | If this is `true` then the path passed to `ServletContext.getResource()` or `ServletContext.getResourceAsStream()` must start with "/". If `false`, code like `getResource("myfolder/myresource.txt")` will work as Tomcat will prepend "/" to the provided path. If `org.apache.catalina.STRICT_SERVLET_COMPLIANCE` is set to `true`, the default of this setting will be `true`, else the default value will be `false`.
`org.apache.catalina.core. ApplicationDispatcher.WRAP_SAME_OBJECT` | If this is `true` then any wrapped request or response object passed to an application dispatcher will be checked to ensure that it has wrapped the original request or response. If `org.apache.catalina.STRICT_SERVLET_COMPLIANCE` is set to `true`, the default of this setting will be `true`, else the default value will be `false`.
`org.apache.tomcat.websocket. STRICT_SPEC_COMPLIANCE` | The default value of this system property is `false`. If this is `true` the default values will be changed for: `org.apache.tomcat.websocket.server#isEnforceNoAddAfterHandshake` (default changes from `false` to `true`)
`org.apache.tomcat.util.http. ServerCookie.STRICT_NAMING` | If this is `true` then the requirements of the Servlet specification that Cookie names must adhere to RFC2109 will be enforced. If this is `false` the naming rules specified in RFC6265 (allow the leading "$") will be used. If `org.apache.catalina.STRICT_SERVLET_COMPLIANCE` is set to `true`, the default of this setting will be `true`, else the default value will be `false`.

### Sessions

Property | Description
--- | ---
`org.apache.catalina.authenticator. Constants.SSO_SESSION_COOKIE_NAME` | An alternative name for the single sign on session cookie. Defaults to `JSESSIONIDSSO`.
`org.apache.catalina.core. StandardHostValve.ACCESS_SESSION` | If this is `true`, every request that is associated with a session will cause the session's last accessed time to be updated regardless of whether or not the request explicitly accesses the session. If `org.apache.catalina.STRICT_SERVLET_COMPLIANCE` is set to `true`, the default of this setting will be `true`, else the default value will be `false`.
`org.apache.catalina.session. StandardSession.ACTIVITY_CHECK` | If this is `true`, Tomcat will track the number of active requests for each session. When determining if a session is valid, any session with at least one active request will always be considered valid. If `org.apache.catalina.STRICT_SERVLET_COMPLIANCE` is set to `true`, the default of this setting will be `true`, else the default value will be `false`.
`org.apache.catalina.session. StandardSession.LAST_ACCESS_AT_START` | If this is `true`, the last accessed time for sessions will be calculated from the beginning of the previous request. If `false`, the last accessed time for sessions will be calculated from the end of the previous request. This also affects how the idle time is calculated. If `org.apache.catalina.STRICT_SERVLET_COMPLIANCE` is set to `true`, the default of this setting will be `true`, else the default value will be `false`.

### Logging

Property | Description
--- | ---
`org.apache.juli.formatter` | If no logging configuration file is specified and no logging configuration class is specified using the `java.util.logging.config.class` and `java.util.logging.config.file` properties the default logging framework `org.apache.juli` will use the default `java.util.logging.SimpleFormatter` for all console output. To simply override the console output formatter, one can use the described property. Example: `-Dorg.apache.juli.formatter=org.apache.juli.OneLineFormatter`
`org.apache.juli. AsyncMaxRecordCount` | The maximum number of log records that the JULI AsyncFileHandler will queue in memory. New records are added to the queue and get asynchronously removed from the queue and written to the files by a single writer thread. When the queue is full and a new record is being logged the log record will be handled based on the `org.apache.juli.AsyncOverflowDropType` setting. The default value is `10000` records. This number represents the global number of records, not on a per handler basis.
`org.apache.juli. AsyncOverflowDropType` | When the queue of log records of the JULI AsyncFileHandler is full, new log records are handled according to the following setting: `1` - the newest record in the queue will be dropped and not logged `2` - the oldest record in the queue will be dropped and not logged `3` - suspend the logging thread until older records got written to the log file and the queue is no longer full. This is the only setting that ensures that no messages get lost. `4` - drop the current log record The default value is `1` (drop the newest record in the queue).
`org.apache.juli. AsyncLoggerPollInterval` | The poll interval in milliseconds for the asynchronous logger thread. If the log queue is empty, the async thread will issue a poll(poll interval) in order to not wake up too often. The default value is `1000` milliseconds.
`org.apache.juli.logging. UserDataHelper.CONFIG` | The type of logging to use for errors generated by invalid input data. The options are: `DEBUG_ALL`, `INFO_THEN_DEBUG`, `INFO_ALL` and `NONE`. When `INFO_THEN_DEBUG` is used, the period for which errors are logged at DEBUG rather than INFO is controlled by the system property `org.apache.juli.logging.UserDataHelper.SUPPRESSION_TIME`. The default value is `INFO_THEN_DEBUG`. The errors currently logged using this system are: invalid cookies; invalid parameters; too many headers, too many parameters (hitting `maxHeaderCount` or `maxParameterCount` limits of a connector). invalid host names Other errors triggered by invalid input data may be added to this system in later versions.
`org.apache.juli.logging. UserDataHelper.SUPPRESSION_TIME` | When using `INFO_THEN_DEBUG` for `org.apache.juli.logging.UserDataHelper.CONFIG` this system property controls how long messages are logged at DEBUG after a message has been logged at INFO. Once this period has elapsed, the next message will be logged at INFO followed by a new suppression period where messages are logged at DEBUG and so on. The value is measured in seconds. A value of `0` is equivalent to using `INFO_ALL` for `org.apache.juli.logging.UserDataHelper.CONFIG`. A negative value means an infinite suppression period. The default value is `86400` (24 hours).

### JAR Scanning

Property | Description
--- | ---
`tomcat.util.scan. StandardJarScanFilter.jarsToSkip` | A list of comma-separated file name patters that is used as the default value for `pluggabilitySkip` and `tldSkip` attributes of the standard JarScanFilter implementation. The coded default is empty, however the system property is set in a default Tomcat installation via the `$CATALINA_BASE/conf/catalina.properties` file.
`tomcat.util.scan. StandardJarScanFilter.jarsToScan` | A list of comma-separated file name patters that is used as the default value for `pluggabilityScan` and `tldScan` attributes of the standard JarScanFilter implementation. The coded default is empty, however the system property is set in a default Tomcat installation via the `$CATALINA_BASE/conf/catalina.properties` file.

### Websockets

Property | Description
--- | ---
`org.apache.tomcat. websocket.ALLOW_UNSUPPORTED_EXTENSIONS` | If `true`, allow unknown extensions to be declared by the user. The default value is `false`.
`org.apache.tomcat. websocket.DEFAULT_BUFFER_SIZE` | The default size for buffers used in the Websockets container. The default value is `8192` which corresponds to 8KB.
`org.apache.tomcat. websocket.DEFAULT_ORIGIN_HEADER_VALUE` | Default value of the origin header that will be sent by the client during the upgrade handshake. The default is null so that no origin header is sent.
`org.apache.tomcat. websocket.DEFAULT_PROCESS_PERIOD` | The number of periodic ticks between periodic processing which involves in particular session expiration checks. The default value is `10` which corresponds to 10 seconds.
`org.apache.tomcat. websocket.DISABLE_BUILTIN_EXTENSIONS` | If `true`, disable all built-in extensions provided by the server, such as message compression. The default value is `false`.

### Other

Property | Description
--- | ---
`catalina.useNaming` | If this is `false` it will override the `useNaming` attribute for all Context elements.
`javax.sql.DataSource.Factory` | The class name of the factory to use to create resources of type `javax.sql.DataSource`. If not specified the default of `org.apache.tomcat.dbcp.dbcp2.BasicDataSourceFactory` is used which is a package renamed (to avoid conflicts) copy of Apache Commons DBCP 2.
`javax.mail.Session.Factory` | The class name of the factory to use to create resources of type `javax.mail.Session`. If not specified the default of `org.apache.naming.factory.MailSessionFactory` is used.
`jvmRoute` | Provides a default value for the `jvmRoute` attribute of the Engine element. It does not override the value configured on the Engine element.
`catalina.config` | The location from which to load the catalina.properties configuration file. This may be an absolute URL, a relative (to the current working directory) URL or an alternative file name in which case Tomcat will attempt to load the file from the default location of `$CATALINA_BASE/conf/`.
`tomcat.util.buf.StringCache.byte.enabled` | If `true`, the String cache is enabled for `ByteChunk`. If not specified, the default value of `false` will be used.
`tomcat.util.buf.StringCache.char.enabled` | If `true`, the String cache is enabled for `CharChunk`. If not specified, the default value of `false` will be used.
`tomcat.util.buf.StringCache.trainThreshold` | The number of times `toString()` must be called before the cache is activated. If not specified, the default value of `20000` will be used.
`tomcat.util.buf.StringCache.cacheSize` | The size of the String cache. If not specified, the default value of `200` will be used.
`org.apache.tomcat.util.buf.UriUtil. WAR_SEPARATOR` | The character to use to separate the WAR file and WAR content parts of a WAR URL using the custom WAR scheme provided by Tomcat. This is equivalent to how `!` is used in JAR URLs. If not specified, the default value of `*` will be used.
`tomcat.util.buf.StringCache.maxStringSize` | The maximum length of String that will be cached. If not specified, the default value of `128` will be used.
`org.apache.tomcat.util. http.FastHttpDateFormat.CACHE_SIZE` | The size of the cache to use parsed and formatted date value. If not specified, the default value of `1000` will be used.
`org.apache.tomcat.util. net.NioSelectorShared` | If `true`, use a shared selector for servlet write/read. If not specified, the default value of `true` will be used.
`org.apache.catalina.startup. EXIT_ON_INIT_FAILURE` | If `true`, the server will exit if an exception happens during the server initialization phase. To support this feature, this system property is used as the default for the throwOnFailure attribute of a Connector. If not specified, the default value of `false` will be used.
`org.apache.catalina.startup. RealmRuleSet.MAX_NESTED_REALM_LEVELS` | The CombinedRealm allows nested Realms. This property controls the maximum permitted number of levels of nesting. If not specified, the default value of `3` will be used.
`org.apache.catalina.startup. CredentialHandlerRuleSet.MAX_NESTED_LEVELS` | The NestedCredentialHandler allows nested CredentialHandlers. This property controls the maximum permitted number of levels of nesting. If not specified, the default value of `3` will be used.