因為jasper server中Multi-Select控件得到的值不是String,，而是Collection。這些值可以顯示在report中或者打印出來。但是當Multi-Select中的值用到sql query中必須是String，所以需要把它轉換成String list.
先建立一個parameter，類型為java.util.Collection。可以設定 default value 為
Arrays.asList(new Integer[] 
{Integer.valueOf(1), Integer.valueOf(2) } )
或者
Arrays.asList(new String[] {"entry1", "entry2" })然后建立另一個parameter，類型為String。defaultValueExpression為下面其中的一個
$P{MultiTaskInput}.toString().replaceAll("[\\[\\]]", "")//for integer
或者
$P{MultiTaskInput}.toString().replaceAll("[\\[\\]]", "'").replaceAll(", ", "', '")//for String(char in database) 把 , 換成 ' , '
**因為collection的String格式為 [1]，[2]，[3]。所以到把方括號替換掉。
把第二個parameter帶入query中，SQL為
SELECT * FROM TABLE WHERE cloumn in ($P!{param}) //注意 $P后要加！
這樣就可以建立動態query, 數據庫運行select基于parameter中list的值。 類似于
SELECT * FROM table WHERE column IN ('1','3','5')
關于$P!{}的原文解釋：
The $P{} syntax is used for introducing parameter values just like you use the ? in a JDBC prepared statement. They are placeholders for prepared statement parameters.
The $P!{} simply expands the value of the parameter within the query text. It is used for dynamically building queries or for providing the whole query text as a parameter.
The $X{} syntax is a new addition in JR 1.3.2 and is something in between the previous two. It is a way to dynamically build a part of the query, but also introduce parameter placeholders.
There are two $X{} functions supported by the SQL query executer in JasperReports:
$X{IN, colName, paramName}
and
$X{NOTIN, colName, paramName}
paramName should be the name of a report parameter that is either of type Collection or array.
This syntax is to be used in order to produce these SQL sequences in the WHERE clause:
colName IN {val1, val2, ...}
or
colName NOT IN {val1, val2, ...}
where val1, val2, ... are values in the collection or array parameter mentioned.
Check the supplied /demo/sample/query for a working example of this.