module Ice {
struct Identity {
string name;
string category;
};
};
As you can see, an object identity consists of a pair of strings, a name and a
category. The complete object identity is the combination of
name and
category, that is, for two identities to be equal, both
name and
category must be the same. The
category member is usually the empty string, unless you are using servant locators (see
Section 28.7).
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If name is an empty string,
category must be the empty string as well. (An identity with an empty
name and a non-empty
category is illegal.) If a proxy contains an identity in which
name is empty, Ice interprets that proxy as a null proxy.
Object identities can be represented as strings; the category part appears first and is followed by the
name; the two components are separated by a
/ character, for example:
In this example, Factory is the
category, and
File is the
name. If the
name or
category member themselves contain a
/ character, the stringified representation escapes the
/ character with a
\, for example:
In this example, the category member is
Factories/Factory and the
name member is
Node/File.
You rarely need to write identities as strings because, typically, your code will be using
identityToString and
stringToIdentity (see
Section 28.5.2), or simply deal with proxies instead of identities. However, on occasion, you will need to use stringified identities in configuration files. If the identities happen to contain meta-characters (such as a slash or backslash), or characters outside the printable ASCII range, these characters must be escaped in the stringified representation. Here are rules that the Ice run time applies when parsing a stringified identity:
1. The parser scans the stringified identity for an un‑escaped slash character (
/). If such a slash character can be found, the substrings to the left and right of the slash are parsed as the
category and
name members of the identity, respectively; if no such slash character can be found, the entire string is parsed as the
name member of the identity, and the
category member is the empty string.
2.
Each of the category (if present) and
name substrings is parsed according to the following rules:
4. An escape sequence of the form \o,
\oo, or
\ooo (where
o is a digit in the range 0 to 7) is replaced with the ASCII character with the corresponding octal value. Parsing for octal digits allows for at most three consecutive digits, so the string
\0763 is interpreted as the character with octal value 76 (
>) followed by the character
3. Parsing for octal digits terminates as soon as it encounters a character that is not in the range 0 to 7, so
\7x is the character with octal value 7 (bell) followed by the character
x. Octal escape sequences must be in the range 0 to 255 (octal 000 to 377); escape sequences outside this range cause a parsing error. For example,
\539 is an illegal escape sequence.
To make conversion of identities to and from strings easier, the Communicator interface provides appropriate conversion functions:
local interface Communicator {
string identityToString(Identity id);
Identity stringToIdentity(string id);
};
For C++, the operations on the communicator are the only way to convert between identities and strings. For other languages, the conversion functions are provided as operations on the communicator as well but, in addition, the language mappings provide static utility functions. (The utility functions have the advantage that you can call them without holding a reference to the communicator.)
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package Ice;
public final class Util {
public static String identityToString(Identity id);
public static Identity stringToIdentity(String s);
}
namespace Ice
{
public sealed class Util
{
public static string identityToString(Identity id);
public static Identity stringToIdentity(string s);
}
}
As mentioned on page 739, each entry in the ASM for an object adapter must be unique: you cannot add two servants with the same identity to the ASM.
