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Freemarker template files are no more complex than HTML pages, Freemarker template files consist of the following 4 parts:
1, Text: Part of the direct output
2, note: <#--...--> format section, will not output
3, interpolation: That is ${...} Or #{...} Part of the format that replaces the output with the part in the data model
4,FTL directive: Freemarker specified, similar to HTML tags, name before plus # to differentiate, will not output
Here is an example of a freemarker template that contains the 4 parts described above
<title>Welcome!</title><br>
<body><br>
<#--Annotation Section--><br>
<#--use interpolation below-->
<p>we have these animals:<br>
<u1><br>
<#--Use FTL instruction-->
< #list animals as being><br>
<li>${being.name} for ${being.price} euros<br>
< #list ><br>
<u1><br>
</body><br>
1, FTL instruction rules
In Freemarker, using the FTL tag to use instructions, Freemarker has 3 FTL tags, which are exactly like HTML tags.
1, start tag:< #directivename parameter>
2, end tag: </#directivename >
3, empty label:< #directivename parameter/>
In fact, the symbol at the front of the label may also become @, and if the instruction is a user instruction instead of a system-built instruction, the # symbol should be changed to the @ symbol.
When you use the FTL tag, you should have the correct nesting, not the cross use, which is exactly the same as the XML tag. If you use a directive that does not exist, Freemarker does not use the template output, but instead produces an error message. Freemarker ignores whitespace characters in the FTL label. It is noteworthy that there is no white space character allowed between the <,/> and instructions.
2, interpolation rules
Freemarker interpolation has the following two types: 1, universal interpolation ${expr};2, number format interpolation: #{expr} or #{expr;format}
2.1 General interpolation
For universal interpolation, it can be divided into the following 4 kinds of situations:
1, interpolation result is string value: direct Output expression result
2, the interpolation result is a numeric value: The expression result is converted to the text output according to the default format (set by the #setting instruction). You can use built-in string functions to format a single interpolation, as in the following example:
< #settion number_format= "currency"/>
< #assign answer=42/>
${answer}
${answer?string} <#--the same as ${answer}-->
${answer?string.number}
${answer?string.currency}
${answer?string.percent}
${answer}
The output results are:
$42.00
$42.00
42
$42.00
4,200%
3, the interpolation result is a date value: The expression result is converted to the text output according to the default format (set by the #setting instruction). You can use built-in string functions to format a single interpolation, as in the following example:
${lastupdated?string ("Yyyy-mm-dd HH:mm:ss zzzz")}
${lastupdated?string ("EEE, MMM D, ' yy")}
${lastupdated?string ("eeee, MMMM dd, yyyy, HH:MM:SS a ' (' zzz ')")}
The output results are:
2008-04-08 08:08:08 Pacific Daylight Time
Tue, APR 8, ' 03
Tuesday, April, 2003, 08:08:08 PM (PDT)
4, the interpolation result is a Boolean value: The expression result is converted to the text output according to the default format (set by the #setting instruction). You can format a single interpolation using built-in string functions, as in the following example:
< #assign foo=true/>
${foo?string ("Yes", "No")}
The output results are:
Yes
2.2 Number format interpolation
Numeric format interpolation can be formatted with #{expr;format}, where format can be:
MX: Decimal part minimum x bit
MX: Decimal part max x bit
As in the following example:
< #assign x=2.582/>
< #assign y=4/>
#{x; M2} <#--output 2.58-->
#{y; M2} <#--Output 4-->
#{x m2} <#--output 2.6-->
#{y m2} <#--output 4.0-->
#{x m1m2} <#--output 2.58-->
#{x m1m2} <#--Output 4.0-->
3, an expression
The expression is the core function of the Freemarker template, where the expression is placed in the interpolation syntax ${}, indicating that the value of the output expression is required; The expression syntax can also be combined with the freemarker tag to control the output. Actually, the Freemarker expression is very powerful, It supports not only the direct designation of values, output variable values, but also string formatting output and collection access functions.
3.1 Specifying values directly
Use the direct specify value syntax to let freemarker directly output the value in the interpolation, rather than the output variable value. The direct specified value can be a string, a numeric value, a Boolean value, a collection, and a Map object.
1, string
Specify string values directly using single or double quotes to qualify, if the string value contains special characters that need to be escaped, see the following example:
${"My files saved on c:\\ disk"}
${' My name is \ annlee\ '}
The output results are:
My files are saved on the C:\ disk.
My name is "Annlee."
Freemarker supports the following escape characters:
\ "; double quotes (u0022)
\ '; single quotation mark (u0027)
\ n, backslash (u005c)
\ n; line break (u000a)
\ r; carriage return (u000d)
\ t; Tab (u0009)
\b Backspace (u0008)
\f; Form Feed (u000c)
\l;<
\g;>
\a;&
\{; {
\xcode: Specifies the Unicode code directly through a 4-bit 16-digit number, outputting the character corresponding to the Unicode code.
If a paragraph of text contains a large number of special symbols, Freemarker provides another special format: You can add the R tag before the quotation marks in the specified string contents, and the file will be output directly after the R tag. Look at the following code:
${r "${foo}"}
${r "C:\foo\bar"}
The output results are:
${foo}
C:\foo\bar
2, numerical
The values in the expression are output directly, without quotation marks. Decimal use "." Delimited, the grouping "," symbol cannot be used. Freemarker currently does not support scientific notation, so "1E3" is wrong. Using numeric values in Freemarker expressions requires attention to the following points:
1, the value can not omit the decimal point before the 0, so ". 5" is the wrong wording
2, the value 8, +8, 8.00 are the same
3, Boolean value
Use True and false directly, and do not use quotes.
4, set
The collection is enclosed in square brackets, separated by commas "," between the elements of the collection, and look at the following example:
< #list ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"] as X>
${X}
</#list >
The output results are:
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
In addition, the collection element can also be an expression, as in the following example:
[2 + 2, [1, 2, 3, 4], "whatnot"]
You can also use a numeric range to define a set of numbers, such as 2. 5 is equivalent to [2, 3, 4, 5], but more efficient. Note that using a numeric range to define a collection eliminates the need for square brackets, and the range of numbers also supports the inverse of the range of digits, such as 5. 2
5,map objects
The Map object uses curly braces, which are delimited by the English colon ":" between the key-value pairs in the map, separated by the English comma "," for multiple sets of key-value pairs. Here is an example:
{"Language": 78, "math": 80}
