Class MimeHeaders
- java.lang.Object
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- org.apache.tomcat.util.http.MimeHeaders
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public class MimeHeaders extends java.lang.ObjectMemory-efficient repository for Mime Headers. When the object is recycled, it will keep the allocated headers[] and all the MimeHeaderField - no GC is generated.For input headers it is possible to use the MessageByte for Fields - so no GC will be generated.
The only garbage is generated when using the String for header names/values - this can't be avoided when the servlet calls header methods, but is easy to avoid inside tomcat. The goal is to use _only_ MessageByte-based Fields, and reduce to 0 the memory overhead of tomcat.
This class is used to contain standard internet message headers, used for SMTP (RFC822) and HTTP (RFC2068) messages as well as for MIME (RFC 2045) applications such as transferring typed data and grouping related items in multipart message bodies.
Message headers, as specified in RFC822, include a field name and a field body. Order has no semantic significance, and several fields with the same name may exist. However, most fields do not (and should not) exist more than once in a header.
Many kinds of field body must conform to a specified syntax, including the standard parenthesized comment syntax. This class supports only two simple syntaxes, for dates and integers.
When processing headers, care must be taken to handle the case of multiple same-name fields correctly. The values of such fields are only available as strings. They may be accessed by index (treating the header as an array of fields), or by name (returning an array of string values).
Headers are first parsed and stored in the order they are received. This is based on the fact that most servlets will not directly access all headers, and most headers are single-valued. (the alternative - a hash or similar data structure - will add an overhead that is not needed in most cases)
Apache seems to be using a similar method for storing and manipulating headers.
- Author:
- dac@eng.sun.com, James Todd [gonzo@eng.sun.com], Costin Manolache, kevin seguin
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Field Summary
Fields Modifier and Type Field Description static intDEFAULT_HEADER_SIZEInitial size - should be == average number of headers per request
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Constructor Summary
Constructors Constructor Description MimeHeaders()Creates a new MimeHeaders object using a default buffer size.
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Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description MessageBytesaddValue(byte[] b, int startN, int len)Create a new named header using un-translated byte[].MessageBytesaddValue(java.lang.String name)Create a new named header , return the MessageBytes container for the new valuevoidclear()Deprecated.voidduplicate(MimeHeaders source)intfindHeader(java.lang.String name, int starting)Find the index of a header with the given name.java.lang.StringgetHeader(java.lang.String name)MessageBytesgetName(int n)MessageBytesgetUniqueValue(java.lang.String name)Finds and returns a unique header field with the given name.MessageBytesgetValue(int n)MessageBytesgetValue(java.lang.String name)Finds and returns a header field with the given name.java.util.Enumeration<java.lang.String>names()Returns an enumeration of strings representing the header field names.voidrecycle()Clears all header fields.voidremoveHeader(int idx)Reset, move to the end and then reduce count by 1.voidremoveHeader(java.lang.String name)Removes a header field with the specified name.voidsetLimit(int limit)Set limit on the number of header fields.MessageBytessetValue(java.lang.String name)Allow "set" operations, which removes all current values for this header.intsize()java.lang.StringtoString()java.util.Enumeration<java.lang.String>values(java.lang.String name)
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Field Detail
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DEFAULT_HEADER_SIZE
public static final int DEFAULT_HEADER_SIZE
Initial size - should be == average number of headers per request- See Also:
- Constant Field Values
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Method Detail
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setLimit
public void setLimit(int limit)
Set limit on the number of header fields.- Parameters:
limit- The new limit
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recycle
public void recycle()
Clears all header fields.
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clear
@Deprecated public void clear()
Deprecated.
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toString
public java.lang.String toString()
- Overrides:
toStringin classjava.lang.Object
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duplicate
public void duplicate(MimeHeaders source) throws java.io.IOException
- Throws:
java.io.IOException
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size
public int size()
- Returns:
- the current number of header fields.
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getName
public MessageBytes getName(int n)
- Parameters:
n- The header index- Returns:
- the Nth header name, or null if there is no such header. This may be used to iterate through all header fields.
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getValue
public MessageBytes getValue(int n)
- Parameters:
n- The header index- Returns:
- the Nth header value, or null if there is no such header. This may be used to iterate through all header fields.
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findHeader
public int findHeader(java.lang.String name, int starting)Find the index of a header with the given name.- Parameters:
name- The header namestarting- Index on which to start looking- Returns:
- the header index
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names
public java.util.Enumeration<java.lang.String> names()
Returns an enumeration of strings representing the header field names. Field names may appear multiple times in this enumeration, indicating that multiple fields with that name exist in this header.- Returns:
- the enumeration
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values
public java.util.Enumeration<java.lang.String> values(java.lang.String name)
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addValue
public MessageBytes addValue(java.lang.String name)
Create a new named header , return the MessageBytes container for the new value- Parameters:
name- The header name- Returns:
- the message bytes container for the value
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addValue
public MessageBytes addValue(byte[] b, int startN, int len)
Create a new named header using un-translated byte[]. The conversion to chars can be delayed until encoding is known.- Parameters:
b- The header name bytesstartN- Offsetlen- Length- Returns:
- the message bytes container for the value
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setValue
public MessageBytes setValue(java.lang.String name)
Allow "set" operations, which removes all current values for this header.- Parameters:
name- The header name- Returns:
- the message bytes container for the value
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getValue
public MessageBytes getValue(java.lang.String name)
Finds and returns a header field with the given name. If no such field exists, null is returned. If more than one such field is in the header, an arbitrary one is returned.- Parameters:
name- The header name- Returns:
- the value
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getUniqueValue
public MessageBytes getUniqueValue(java.lang.String name)
Finds and returns a unique header field with the given name. If no such field exists, null is returned. If the specified header field is not unique then anIllegalArgumentExceptionis thrown.- Parameters:
name- The header name- Returns:
- the value if unique
- Throws:
java.lang.IllegalArgumentException- if the header has multiple values
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getHeader
public java.lang.String getHeader(java.lang.String name)
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removeHeader
public void removeHeader(java.lang.String name)
Removes a header field with the specified name. Does nothing if such a field could not be found.- Parameters:
name- the name of the header field to be removed
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removeHeader
public void removeHeader(int idx)
Reset, move to the end and then reduce count by 1.- Parameters:
idx- the index of the header to remove.
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