Top Description Inners Fields Constructors Methods
org.springframework.web.servlet.resource

public Class CssLinkResourceTransformer

extends ResourceTransformerSupport
Class Inheritance
Imports
java.io.IOException, .StringWriter, java.nio.charset.Charset, .StandardCharsets, java.util.ArrayList, .List, .SortedSet, .TreeSet, jakarta.servlet.http.HttpServletRequest, org.apache.commons.logging.Log, .LogFactory, org.springframework.core.io.Resource, org.springframework.lang.Nullable, org.springframework.util.FileCopyUtils, .StringUtils
A ResourceTransformer implementation that modifies links in a CSS file to match the public URL paths that should be exposed to clients (e.g. with an MD5 content-based hash inserted in the URL).

The implementation looks for links in CSS @import statements and also inside CSS url() functions. All links are then passed through the ResourceResolverChain and resolved relative to the location of the containing CSS file. If successfully resolved, the link is modified, otherwise the original link is preserved.

Author
Rossen Stoyanchev
Since
4.1

Nested and Inner Type Summary

Modifier and TypeClass and Description
protected abstract static class
CssLinkResourceTransformer.AbstractLinkParser

Abstract base class for LinkParser implementations.

private static class
CssLinkResourceTransformer.ContentChunkInfo

private static class
CssLinkResourceTransformer.ImportStatementLinkParser

protected static interface
CssLinkResourceTransformer.LinkParser

Extract content chunks that represent links.

private static class
CssLinkResourceTransformer.UrlFunctionLinkParser

Field Summary

Modifier and TypeField and Description
private static final Charset
DEFAULT_CHARSET

private final List<CssLinkResourceTransformer.LinkParser>
linkParsers

private static final Log
logger

Constructor Summary

AccessConstructor and Description
public
CssLinkResourceTransformer()

Method Summary

Modifier and TypeMethod and Description
private boolean
hasScheme(String link)

public Resource
transform(HttpServletRequest
the current request
request, Resource
the resource to transform
resource, ResourceTransformerChain
the chain of remaining transformers to delegate to
transformerChain)

Implements org.springframework.web.servlet.resource.ResourceTransformer.transform.

Transform the given resource.

Inherited from org.springframework.web.servlet.resource.ResourceTransformerSupport:
getResourceUrlProviderresolveUrlPathsetResourceUrlProvidertoAbsolutePath

Field Detail

DEFAULT_CHARSETback to summary
private static final Charset DEFAULT_CHARSET
linkParsersback to summary
private final List<CssLinkResourceTransformer.LinkParser> linkParsers
loggerback to summary
private static final Log logger

Constructor Detail

CssLinkResourceTransformerback to summary
public CssLinkResourceTransformer()

Method Detail

hasSchemeback to summary
private boolean hasScheme(String link)
transformback to summary
public Resource transform(HttpServletRequest request, Resource resource, ResourceTransformerChain transformerChain) throws IOException

Implements org.springframework.web.servlet.resource.ResourceTransformer.transform.

Doc from org.springframework.web.servlet.resource.ResourceTransformer.transform.

Transform the given resource.

Parameters
request:HttpServletRequest

the current request

resource:Resource

the resource to transform

transformerChain:ResourceTransformerChain

the chain of remaining transformers to delegate to

Returns:Resource

the transformed resource (never null)

Annotations
@SuppressWarnings:deprecation
@Override
Exceptions
IOException:
if the transformation fails
org.springframework.web.servlet.resource back to summary

protected abstract Class CssLinkResourceTransformer.AbstractLinkParser

extends Object
implements LinkParser
Class Inheritance
  • java.lang.Object
  • org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser
All Implemented Interfaces
org.springframework.web.servlet.resource.CssLinkResourceTransformer.LinkParser
Known Direct Subclasses
org.springframework.web.servlet.resource.CssLinkResourceTransformer.ImportStatementLinkParser, org.springframework.web.servlet.resource.CssLinkResourceTransformer.UrlFunctionLinkParser
Abstract base class for LinkParser implementations.

Constructor Summary

AccessConstructor and Description
protected
AbstractLinkParser()

Method Summary

Modifier and TypeMethod and Description
protected abstract String
getKeyword()

Return the keyword to use to search for links, e.g. "@import", "url("

public void
parse(String content, SortedSet<CssLinkResourceTransformer.ContentChunkInfo> result)

Implements org.springframework.web.servlet.resource.CssLinkResourceTransformer.LinkParser.parse.

Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAlltoStringwaitwaitwait

Constructor Detail

AbstractLinkParserback to summary
protected AbstractLinkParser()

Method Detail

extractLinkback to summary
protected int extractLink(int index, String endKey, String content, SortedSet<CssLinkResourceTransformer.ContentChunkInfo> linksToAdd)
extractLinkback to summary
protected abstract int extractLink(int index, String content, SortedSet<CssLinkResourceTransformer.ContentChunkInfo> linksToAdd)

Invoked after a keyword match, after whitespace has been removed, and when the next char is neither a single nor double quote.

getKeywordback to summary
protected abstract String getKeyword()

Return the keyword to use to search for links, e.g. "@import", "url("

parseback to summary
public void parse(String content, SortedSet<CssLinkResourceTransformer.ContentChunkInfo> result)

Implements org.springframework.web.servlet.resource.CssLinkResourceTransformer.LinkParser.parse.

Annotations
@Override
org.springframework.web.servlet.resource back to summary

private Class CssLinkResourceTransformer.ContentChunkInfo

extends Object
implements Comparable<CssLinkResourceTransformer.ContentChunkInfo>
Class Inheritance
  • java.lang.Object
  • org.springframework.web.servlet.resource.CssLinkResourceTransformer.ContentChunkInfo
All Implemented Interfaces
java.lang.Comparable

Field Summary

Modifier and TypeField and Description
private final int
end

private final int
start

Constructor Summary

AccessConstructor and Description
pack-priv
ContentChunkInfo(int start, int end)

Method Summary

Modifier and TypeMethod and Description
public int
compareTo(CssLinkResourceTransformer.ContentChunkInfo
the object to be compared.
other)

Implements java.lang.Comparable.compareTo.

Compares this object with the specified object for order.

public boolean
equals(Object
the reference object with which to compare.
other)

Overrides java.lang.Object.equals.

Indicates whether some other object is "equal to" this one.

public int
getEnd()

public int
getStart()

public int
hashCode()

Overrides java.lang.Object.hashCode.

Returns a hash code value for this object.

Inherited from java.lang.Object:
clonefinalizegetClassnotifynotifyAlltoStringwaitwaitwait

Field Detail

endback to summary
private final int end
startback to summary
private final int start

Constructor Detail

ContentChunkInfoback to summary
pack-priv ContentChunkInfo(int start, int end)

Method Detail

compareToback to summary
public int compareTo(CssLinkResourceTransformer.ContentChunkInfo other)

Implements java.lang.Comparable.compareTo.

Doc from java.lang.Comparable.compareTo.

Compares this object with the specified object for order. Returns a negative integer, zero, or a positive integer as this object is less than, equal to, or greater than the specified object.

The implementor must ensure signum(x.compareTo(y)) == -signum(y.compareTo(x)) for all x and y. (This implies that x.compareTo(y) must throw an exception if and only if y.compareTo(x) throws an exception.)

The implementor must also ensure that the relation is transitive: (x.compareTo(y) > 0 && y.compareTo(z) > 0) implies x.compareTo(z) > 0.

Finally, the implementor must ensure that x.compareTo(y)==0 implies that signum(x.compareTo(z)) == signum(y.compareTo(z)), for all z.

Parameters
other:CssLinkResourceTransformer.ContentChunkInfo

the object to be compared.

Returns:int

a negative integer, zero, or a positive integer as this object is less than, equal to, or greater than the specified object.

Annotations
@Override
equalsback to summary
public boolean equals(Object other)

Overrides java.lang.Object.equals.

Doc from java.lang.Object.equals.

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

  • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
  • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
  • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
  • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
  • For any non-null reference value x, x.equals(null) should return false.

An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes.

Parameters
other:Object

the reference object with which to compare.

Returns:boolean

true if this object is the same as the obj argument; false otherwise.

Annotations
@Override
getEndback to summary
public int getEnd()
getStartback to summary
public int getStart()
hashCodeback to summary
public int hashCode()

Overrides java.lang.Object.hashCode.

Doc from java.lang.Object.hashCode.

Returns a hash code value for this object. This method is supported for the benefit of hash tables such as those provided by java.util.HashMap.

The general contract of hashCode is:

  • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
  • If two objects are equal according to the equals method, then calling the hashCode method on each of the two objects must produce the same integer result.
  • It is not required that if two objects are unequal according to the equals method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
Returns:int

a hash code value for this object

Annotations
@Override
org.springframework.web.servlet.resource back to summary

private Class CssLinkResourceTransformer.ImportStatementLinkParser

extends AbstractLinkParser
Class Inheritance

Constructor Summary

AccessConstructor and Description
private
ImportStatementLinkParser()

Method Summary

Modifier and TypeMethod and Description
protected String
getKeyword()

Implements abstract org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.getKeyword.

Return the keyword to use to search for links, e.g. "@import", "url("

Inherited from org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser:
extractLinkparse

Constructor Detail

ImportStatementLinkParserback to summary
private ImportStatementLinkParser()

Method Detail

extractLinkback to summary
protected int extractLink(int index, String content, SortedSet<CssLinkResourceTransformer.ContentChunkInfo> linksToAdd)

Implements abstract org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.extractLink.

Doc from org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.extractLink.

Invoked after a keyword match, after whitespace has been removed, and when the next char is neither a single nor double quote.

Annotations
@Override
getKeywordback to summary
protected String getKeyword()

Implements abstract org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.getKeyword.

Doc from org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.getKeyword.

Return the keyword to use to search for links, e.g. "@import", "url("

Annotations
@Override
org.springframework.web.servlet.resource back to summary

protected Interface CssLinkResourceTransformer.LinkParser

Known Direct Implementers
org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser
Annotations
@FunctionalInterface
Extract content chunks that represent links.

Method Summary

Modifier and TypeMethod and Description
public void
parse(String content, SortedSet<CssLinkResourceTransformer.ContentChunkInfo> result)

Method Detail

parseback to summary
public void parse(String content, SortedSet<CssLinkResourceTransformer.ContentChunkInfo> result)
org.springframework.web.servlet.resource back to summary

private Class CssLinkResourceTransformer.UrlFunctionLinkParser

extends AbstractLinkParser
Class Inheritance

Constructor Summary

AccessConstructor and Description
private
UrlFunctionLinkParser()

Method Summary

Modifier and TypeMethod and Description
protected String
getKeyword()

Implements abstract org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.getKeyword.

Return the keyword to use to search for links, e.g. "@import", "url("

Inherited from org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser:
extractLinkparse

Constructor Detail

UrlFunctionLinkParserback to summary
private UrlFunctionLinkParser()

Method Detail

extractLinkback to summary
protected int extractLink(int index, String content, SortedSet<CssLinkResourceTransformer.ContentChunkInfo> linksToAdd)

Implements abstract org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.extractLink.

Doc from org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.extractLink.

Invoked after a keyword match, after whitespace has been removed, and when the next char is neither a single nor double quote.

Annotations
@Override
getKeywordback to summary
protected String getKeyword()

Implements abstract org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.getKeyword.

Doc from org.springframework.web.servlet.resource.CssLinkResourceTransformer.AbstractLinkParser.getKeyword.

Return the keyword to use to search for links, e.g. "@import", "url("

Annotations
@Override