Interface SafeHtml
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- All Superinterfaces:
java.io.Serializable
- All Known Implementing Classes:
OnlyToBeUsedInGeneratedCodeStringBlessedAsSafeHtml
,SafeHtmlString
public interface SafeHtml extends java.io.Serializable
An object that implements this interface encapsulates HTML that is guaranteed to be safe to use (with respect to potential Cross-Site-Scripting vulnerabilities) in an HTML context.Note on usage: SafeHtml should be used to ensure user input is not executed in the browser. SafeHtml should not be used to sanitize input before sending it to the server: The server cannot rely on the type contract of SafeHtml values received from clients, because a malicious client could provide maliciously crafted serialized forms of implementations of this type that violate the type contract.
All implementing classes must maintain the class invariant (by design and implementation and/or convention of use), that invoking
asString()
on any instance will return a string that is safe to assign to the.innerHTML
DOM property in a browser (or to use similarly in an "inner HTML" context), in the sense that doing so must not cause execution of script in the browser.Furthermore, values of this type must be composable, i.e. for any two values
A
andB
of this type,A.asString() + B.asString()
must itself be a value that satisfies the SafeHtml type constraint. This requirement implies that for any valueA
of this type, ifA.asString()
includes HTML markup, the string must end in an "inner HTML" context and not inside a tag or attribute. For example, a value of<div style="
or<img src="
would not satisfy the SafeHtml contract. This is because concatenating such strings with a second value that itself does not contain script-executing HTML markup can result in an overall string that does. For example, ifjavascript:malicious()">
is appended to<img src="
, the resulting string may result in script execution.All implementations must implement equals() and hashCode() to behave consistently with the result of asString().equals() and asString.hashCode().
Implementations must not return
null
fromasString()
.
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description java.lang.String
asString()
Returns this object's contained HTML as a string.boolean
equals(java.lang.Object anObject)
Compares this string to the specified object.int
hashCode()
Returns a hash code for this string.
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Method Detail
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asString
java.lang.String asString()
Returns this object's contained HTML as a string.Based on this class' contract, the returned value will be non-null and a string that is safe to use in an HTML context.
- Returns:
- the contents as a String
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equals
boolean equals(java.lang.Object anObject)
Compares this string to the specified object. Must be equal to asString().equals().- Overrides:
equals
in classjava.lang.Object
- Parameters:
anObject
- the object to compare to
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hashCode
int hashCode()
Returns a hash code for this string. Must be equal to asString().hashCode().- Overrides:
hashCode
in classjava.lang.Object
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