## System Properties

### Table of Contents

- Introduction
- Property replacements
- Clustering
- Expression Language
- Jasper
- Security
- Specifications
- Sessions
- Logging
- JAR Scanning
- 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 fully qualified name of a class that implements `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}` denoted parameters are found in the XML files that Tomcat parses.

### Clustering

Property | Description
--- | ---
`org.apache.catalina. tribes.dns_lookups` | 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_QUOTE_ESCAPING` | If `false` the requirements for escaping quotes in JSP attributes will be relaxed so that an unescaped quote will not cause an error. If not specified, the specification compliant default of `true` 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.LIMIT_BUFFER` | If `true`, any tag buffer that expands beyond `org.apache.jasper.Constants.DEFAULT_TAG_BUFFER_SIZE` will be destroyed and a new buffer created of the default size. 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.
`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 jsp pages. 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` | If this is `true` '%2F' and '%5C' will be permitted as path delimiters. If not specified, the default value of `false` will be used.

### 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.ALWAYS_ADD_EXPIRES` `org.apache.tomcat.util.http. ServerCookie.FWD_SLASH_IS_SEPARATOR` `org.apache.tomcat.util.http. ServerCookie.STRICT_NAMING` The `URIEncoding` attribute of any HTTP connector or AJP connectorelement. The `resourceOnlyServlets` attribute of any Context element. The `tldValidation` attribute of any Context element. The `xmlNamespaceAware` attribute of any Context element. The `xmlValidation` attribute of any Context element. Note that changing a number of the above defaults is likely to break the majority of systems as some browsers are unable to correctly handle the cookie headers that result from a strict adherence to the specifications. Defaults, regardless of whether or not they have been changed by setting `org.apache.catalina.STRICT_SERVLET_COMPLIANCE` can always be overridden by explicitly setting the appropriate system property or element attribute.
`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. 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.ALLOW_EQUALS_IN_VALUE` | If this is `true` Tomcat will allow '`=`' characters when parsing unquoted cookie values. If `false`, cookie values containing '`=`' will be terminated when the '`=`' is encountered and the remainder of the cookie value will be dropped. If not specified, the default value specification compliant value of `false` will be used.
`org.apache.tomcat.util.http. ServerCookie.ALLOW_HTTP_SEPARATORS_IN_V0` | If this is `true` Tomcat will allow HTTP separators in cookie names and values. If not specified, the default specification compliant value of `false` will be used.
`org.apache.tomcat.util.http. ServerCookie.ALWAYS_ADD_EXPIRES` | If this is `true` Tomcat will always add an expires parameter to a SetCookie header even for cookies with version greater than zero. This is to work around a known IE6 and IE7 bug that causes IE to ignore the Max-Age parameter in a SetCookie header. If `org.apache.catalina.STRICT_SERVLET_COMPLIANCE` is set to `true`, the default of this setting will be `false`, else the default value will be `true`.
`org.apache.tomcat.util.http. ServerCookie.FWD_SLASH_IS_SEPARATOR` | If this is true then the `/` (forward slash) character will be treated as a separator. Note that this character is frequently used in cookie path attributes and some browsers will fail to process a cookie if the path attribute is quoted as is required by a strict adherence to the specifications. This is highly likely to break session tracking using cookies. 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.util.http. ServerCookie.STRICT_NAMING` | If this is true then the requirements of the Servlet specification that Cookie names must adhere to RFC2109 (no use of separators) will be enforced. 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.util.http. ServerCookie.ALLOW_NAME_ONLY` | If this is true then the requirements of the cookie specifications that cookies must have values will be enforced and cookies consisting only of a name but no value will be ignored. If not specified, the default specification compliant value of `false` will be used.

### 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. AsyncOverflowDropType` | When the memory limit of records has been reached the system needs to determine what action to take. Currently there are three actions that can be taken: `int OVERFLOW_DROP_LAST = 1` - the record that caused the overflow will be dropped and not logged `int OVERFLOW_DROP_FIRST = 2` - the record that is next in line to be logged will be dropped to make room for the latest record on the queue `int OVERFLOW_DROP_FLUSH = 3` - suspend the thread while the queue empties out and flushes the entries to the write buffer `int OVERFLOW_DROP_CURRENT = 4` - drop the current log entry The default value is `1` (OVERFLOW_DROP_LAST).
`org.apache.juli. AsyncMaxRecordCount` | The max number of log records that the async logger will keep in memory. When this limit is reached and a new record is being logged by the JULI framework the system will take an action 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. AsyncLoggerPollInterval` | The poll interval in milliseconds for the asynchronous logger thread in milliseconds. 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). 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. DefaultJarScanner.jarsToSkip` | The comma-separated list of filenames of JARs that Tomcat will not scan for configuration information when using the JarScanner functionality. Note that there are additional system properties that enable JARs to be excluded from specific scans rather than all scans. The coded default is that no JARs are skipped however the system property is set in a default Tomcat installation via the `$CATALINA_BASE/conf/catalina.properties` file.
`org.apache.catalina.startup. ContextConfig.jarsToSkip` | The comma-separated list of additional filenames of JARs that Tomcat will not scan for Servlet 3.0 pluggability features. The coded default is that no JARs are skipped however the system property is set in a default Tomcat installation via the `$CATALINA_BASE/conf/catalina.properties` file.

### Other

Property | Description
--- | ---
`org.apache.coyote. USE_CUSTOM_STATUS_MSG_IN_HEADER` | If this is `true`, custom HTTP status messages will be used within HTTP headers. If a custom message is specified that is not valid for use in an HTTP header (as defined by RFC2616) then the custom message will be ignored and the default message used. If not specified, the default value of `false` will be used.
`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 conflictions) copy of Apache Commons DBCP.
`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 URL for the catalina.properties configuration file.
`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.
`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. 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.

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