在开发中很容易忽视一点，输入一个值(可能是小数)，输出时如果不做处理，就很容易出现
隐形的BUG。比如，如果从数据库取出一个0.22的数值，一般的输出${x?if_exists?html},
这时是显示0，而不是0.22。
应该写成${x?if_exists?string.number} 或者 ${x?if_exists.toString()?html}
下面就是关于数字的具体介绍：
Built-ins for numbers
Related FAQs: Do you have things like 1,000,000 or 1 000 000instead of 1000000, or something like 3.14 instead of 3,14 or viceversa? See this and this FAQ entry, also note the c built-in above.
c
Note
This built-in exists since FreeMarker 2.3.3.
This built-in converts a number to string for ``computer audience''as opposed to human audience. That is, it formats with the rules thatprogramming languages used to use, which is independent of all thelocale and number format settings of FreeMarker. It always uses dot asdecimal separator, and it never uses grouping separators (like3,000,000), nor exponential form (like 5E20), nor superfluous leadingor trailing 0-s (like 03 or 1.0), nor + sign (like +1). It will printat most 16 digits after the decimal dot, and thus numbers whoseabsolute value is less than 1E-16 will be shown as 0. This built-in iscrucial because be default (like with ${x}) numbers are converted tostrings with the locale (language, country) specific number formatting,which is for human readers (like 300000 is possibly printed as3,000,000). When the number is printed not for human audience (e.g.,for a database record ID used as the part of an URL, or as invisiblefield value in a HTML form, or for printing CSS/JavaScript numericalliterals) this built-in must be used to print the number (i.e., use${x?c} instead of ${x}), or else the output will be possibly brokendepending on the current number formatting settings and locale (likethe decimal point is not dot, but comma in many countries) and thevalue of the number (like big numbers are possibly ``damaged'' bygrouping separators).
string (when used with a numerical value)
Converts a number to a string. It uses the default format that theprogrammer has specified. You can also specify a number formatexplicitly with this built-in, as it will be shown later.
There are three predefined number formats: number, currency, andpercent. The exact meaning of these is locale (nationality) specific,and is controlled by the Java platform installation, rather than byFreeMarker. You can use these predefined formats like this:
<#assign x=42>
${x}
${x?string} <#-- the same as ${x} -->
${x?string.number}
${x?string.currency}
${x?string.percent}
If your locale is US English, this will certainly produce:
42
42
42
$42.00
4,200%
The output of first three expressions is identical because thefirst two expressions use the default format, which is "number" here.You can change this default using a setting:
<#setting number_format="currency">
<#assign x=42>
${x}
${x?string} <#-- the same as ${x} -->
${x?string.number}
${x?string.currency}
${x?string.percent}
Will now output:
$42.00
$42.00
42
$42.00
4,200%
since the default number format was set to "currency".
Beside the three predefined formats, you can use arbitrary number format patterns written in Java decimal number format syntax:
<#assign x = 1.234>
${x?string("0")}
${x?string("0.#")}
${x?string("0.##")}
${x?string("0.###")}
${x?string("0.####")}
${1?string("000.00")}
${12.1?string("000.00")}
${123.456?string("000.00")}
${1.2?string("0")}
${1.8?string("0")}
${1.5?string("0")} <-- 1.5, rounded towards even neighbor
${2.5?string("0")} <-- 2.5, rounded towards even neighbor
${12345?string("0.##E0")}
outputs this:
1
1.2
1.23
1.234
1.234
001.00
012.10
123.46
1
2
2 <-- 1.5, rounded towards even neighbor
2 <-- 2.5, rounded towards even neighbor
1.23E4
Following the financial and statistics practice, the rounding goesaccording the so called half-even rule, which means rounding towardsthe nearest ``neighbor'', unless both neighbors are equidistant, inwhich case, it rounds towards the even neighbor. This was visible inthe above example if you look at the rounding of 1.5 and of 2.5, asboth were rounded to 2, since 2 is even, but 1 and 3 are odds.
Appart from the Java decimal syntax patterns, you can also write${aNumber?string("currency")} and like, that will do the same as${aNumber?string.currency} and like.
As it was shown for the predefined formats earlier, the default formatting of the numbers can be set in the template:
<#setting number_format="0.##">
${1.234}
outputs this:
1.23
Note that the number formatting is locale sensitive:
<#setting locale="en_US">
US people write: ${12345678?string(",##0.00")}
<#setting locale="hu">
Hungarian people write: ${12345678?string(",##0.00")}
outputs this:
US people write: 12,345,678.00
Hungarian people write: 12 345 678,00
You can find information about the formatting of dates here.
round, floor, ceiling
Note
The rounding built-ins exist since FreeMarker 2.3.13.
Converts a number to a whole number using the specified rounding rule:
*
round: Rounds to the nearest whole number. If the number endswith .5, then it rounds upwards (i.e., towards positive infinity)
*
floor: Rounds the number downwards (i.e., towards neagative infinity)
*
ceiling: Rounds the number upwards (i.e., towards positive infinity)
Example:
<#assign testlist=[
0, 1, -1, 0.5, 1.5, -0.5,
-1.5, 0.25, -0.25, 1.75, -1.75]>
<#list testlist as result>
${result} ?floor=${result?floor} ?ceiling=${result?ceiling} ?round=${result?round}
</#list>
Prints:
0 ?floor=0 ?ceiling=0 ?round=0
1 ?floor=1 ?ceiling=1 ?round=1
-1 ?floor=-1 ?ceiling=-1 ?round=-1
0.5 ?floor=0 ?ceiling=1 ?round=1
1.5 ?floor=1 ?ceiling=2 ?round=2
-0.5 ?floor=-1 ?ceiling=0 ?round=0
-1.5 ?floor=-2 ?ceiling=-1 ?round=-1
0.25 ?floor=0 ?ceiling=1 ?round=0
-0.25 ?floor=-1 ?ceiling=0 ?round=0
1.75 ?floor=1 ?ceiling=2 ?round=2
-1.75 ?floor=-2 ?ceiling=-1 ?round=-2
These built-ins may be useful in pagination operations and like. Ifyou just want to display numbers in rounded form, then you shouldrather use the string built-in or the number_format setting.
隐形的BUG。比如，如果从数据库取出一个0.22的数值，一般的输出${x?if_exists?html},
这时是显示0，而不是0.22。
应该写成${x?if_exists?string.number} 或者 ${x?if_exists.toString()?html}
下面就是关于数字的具体介绍：
Built-ins for numbers
Related FAQs: Do you have things like 1,000,000 or 1 000 000instead of 1000000, or something like 3.14 instead of 3,14 or viceversa? See this and this FAQ entry, also note the c built-in above.
c
Note
This built-in exists since FreeMarker 2.3.3.
This built-in converts a number to string for ``computer audience''as opposed to human audience. That is, it formats with the rules thatprogramming languages used to use, which is independent of all thelocale and number format settings of FreeMarker. It always uses dot asdecimal separator, and it never uses grouping separators (like3,000,000), nor exponential form (like 5E20), nor superfluous leadingor trailing 0-s (like 03 or 1.0), nor + sign (like +1). It will printat most 16 digits after the decimal dot, and thus numbers whoseabsolute value is less than 1E-16 will be shown as 0. This built-in iscrucial because be default (like with ${x}) numbers are converted tostrings with the locale (language, country) specific number formatting,which is for human readers (like 300000 is possibly printed as3,000,000). When the number is printed not for human audience (e.g.,for a database record ID used as the part of an URL, or as invisiblefield value in a HTML form, or for printing CSS/JavaScript numericalliterals) this built-in must be used to print the number (i.e., use${x?c} instead of ${x}), or else the output will be possibly brokendepending on the current number formatting settings and locale (likethe decimal point is not dot, but comma in many countries) and thevalue of the number (like big numbers are possibly ``damaged'' bygrouping separators).
string (when used with a numerical value)
Converts a number to a string. It uses the default format that theprogrammer has specified. You can also specify a number formatexplicitly with this built-in, as it will be shown later.
There are three predefined number formats: number, currency, andpercent. The exact meaning of these is locale (nationality) specific,and is controlled by the Java platform installation, rather than byFreeMarker. You can use these predefined formats like this:
<#assign x=42>
${x}
${x?string} <#-- the same as ${x} -->
${x?string.number}
${x?string.currency}
${x?string.percent}
If your locale is US English, this will certainly produce:
42
42
42
$42.00
4,200%
The output of first three expressions is identical because thefirst two expressions use the default format, which is "number" here.You can change this default using a setting:
<#setting number_format="currency">
<#assign x=42>
${x}
${x?string} <#-- the same as ${x} -->
${x?string.number}
${x?string.currency}
${x?string.percent}
Will now output:
$42.00
$42.00
42
$42.00
4,200%
since the default number format was set to "currency".
Beside the three predefined formats, you can use arbitrary number format patterns written in Java decimal number format syntax:
<#assign x = 1.234>
${x?string("0")}
${x?string("0.#")}
${x?string("0.##")}
${x?string("0.###")}
${x?string("0.####")}
${1?string("000.00")}
${12.1?string("000.00")}
${123.456?string("000.00")}
${1.2?string("0")}
${1.8?string("0")}
${1.5?string("0")} <-- 1.5, rounded towards even neighbor
${2.5?string("0")} <-- 2.5, rounded towards even neighbor
${12345?string("0.##E0")}
outputs this:
1
1.2
1.23
1.234
1.234
001.00
012.10
123.46
1
2
2 <-- 1.5, rounded towards even neighbor
2 <-- 2.5, rounded towards even neighbor
1.23E4
Following the financial and statistics practice, the rounding goesaccording the so called half-even rule, which means rounding towardsthe nearest ``neighbor'', unless both neighbors are equidistant, inwhich case, it rounds towards the even neighbor. This was visible inthe above example if you look at the rounding of 1.5 and of 2.5, asboth were rounded to 2, since 2 is even, but 1 and 3 are odds.
Appart from the Java decimal syntax patterns, you can also write${aNumber?string("currency")} and like, that will do the same as${aNumber?string.currency} and like.
As it was shown for the predefined formats earlier, the default formatting of the numbers can be set in the template:
<#setting number_format="0.##">
${1.234}
outputs this:
1.23
Note that the number formatting is locale sensitive:
<#setting locale="en_US">
US people write: ${12345678?string(",##0.00")}
<#setting locale="hu">
Hungarian people write: ${12345678?string(",##0.00")}
outputs this:
US people write: 12,345,678.00
Hungarian people write: 12 345 678,00
You can find information about the formatting of dates here.
round, floor, ceiling
Note
The rounding built-ins exist since FreeMarker 2.3.13.
Converts a number to a whole number using the specified rounding rule:
*
round: Rounds to the nearest whole number. If the number endswith .5, then it rounds upwards (i.e., towards positive infinity)
*
floor: Rounds the number downwards (i.e., towards neagative infinity)
*
ceiling: Rounds the number upwards (i.e., towards positive infinity)
Example:
<#assign testlist=[
0, 1, -1, 0.5, 1.5, -0.5,
-1.5, 0.25, -0.25, 1.75, -1.75]>
<#list testlist as result>
${result} ?floor=${result?floor} ?ceiling=${result?ceiling} ?round=${result?round}
</#list>
Prints:
0 ?floor=0 ?ceiling=0 ?round=0
1 ?floor=1 ?ceiling=1 ?round=1
-1 ?floor=-1 ?ceiling=-1 ?round=-1
0.5 ?floor=0 ?ceiling=1 ?round=1
1.5 ?floor=1 ?ceiling=2 ?round=2
-0.5 ?floor=-1 ?ceiling=0 ?round=0
-1.5 ?floor=-2 ?ceiling=-1 ?round=-1
0.25 ?floor=0 ?ceiling=1 ?round=0
-0.25 ?floor=-1 ?ceiling=0 ?round=0
1.75 ?floor=1 ?ceiling=2 ?round=2
-1.75 ?floor=-2 ?ceiling=-1 ?round=-2
These built-ins may be useful in pagination operations and like. Ifyou just want to display numbers in rounded form, then you shouldrather use the string built-in or the number_format setting.