在上一個示例
(spring struts ibatis)
的基礎上引入
JFreeChart
組件。
問題：統計各部門員工的人數，并用餅狀或柱狀圖顯示出來。
?
要把
JFreeChart
引入到工程中來，有以下
3
步：
1．?
在
lib
中加入
jcommon-1.0.0.jar, jfreechart-1.0.0.jar
2．?
寫一個
servlet : ChartServlet.java
3．?
在頁面中調用這個
servlet
輸出圖形
.
首先以文本的方式
??????
<
table
>
??????????
<
c:forEach
var
=
"countMap"
items
=
"
${employeeCounts}">
?????????????
<
tr
>
?????????????????
<
td
>
????????????????????
<
c:out
value
=
"
${countMap.DEPT_NAME}"></c:out>
?????????????????
</
td
>
?????????????????
<
td
>
????????????????????
<
c:out
value
=
"
${countMap.EMP_COUNT}"></c:out>
?????????????????
</
td
>
?????????????
</
tr
>
??????????
</
c:forEach
>
??????
</
table
>
再以圖形的方式
<
IMG
src
=
"
<
c:url
value
=
"/chart?type=pie"
/>
"
alt
=
"by Department"
>
<
IMG
src
=
"
<
c:url
value
=
"/chart?type=bar3d"
/>
"
alt
=
"by Department"
>
?
學習筆記：
1．?
起初我嘗試以
IoC
的方式將
Service
注入到
Servlet
中，不成功，后來查資料解決，
詳見：
http://www.jactiongroup.net/spring/viewtopic.php?p=6443
?
2.
第一步是寫
Servlet
?1?public?class?ChartServlet?extends?HttpServlet?{?
?2????????private?EmployeeService?empService;?
?3?
?4????????@Override?
?5????????protected?void?doGet(HttpServletRequest?request,?HttpServletResponse?response)?
?6??????????????????????throws?ServletException,?IOException?{?
?7???????????????doPost(request,?response);?
?8????????}?
?9?
10????????@Override?
11????????protected?void?doPost(HttpServletRequest?request,?
12??????????????????????HttpServletResponse?response)?throws?ServletException,?IOException?{?
13???????????????WebApplicationContext?wac?=?WebApplicationContextUtils?
14?
15?????????????????????????????.getRequiredWebApplicationContext(getServletContext());?
16???????????????empService?=?(EmployeeService)?wac.getBean("employeeService");?
17???????????????String?chartType?=?request.getParameter("type").toUpperCase();?
18???????????????response.setContentType("image/jpeg");?
19???????????????JFreeChart?chart?=?getChart(chartType);?
20???????????????ChartUtilities.writeChartAsJPEG(response.getOutputStream(),?100,?chart,?
21?
22?????????????????????????????400,?300,?null);?
23????????}?
24?
25????????public?JFreeChart?getChart(String?type)?{?
26???????????????List?list?=?empService.getEmployeeCounts();?
27???????????????JFreeChart?chart?=?null;?
28???????????????if?(type.indexOf("PIE")?==?0)?{?
29??????????????????????DefaultPieDataset?data?=?new?DefaultPieDataset();?
30??????????????????????Iterator?it?=?list.iterator();?
31??????????????????????while?(it.hasNext())?{?
32?????????????????????????????Map?m?=?(Map)?it.next();?
33?????????????????????????????data.setValue((String)?m.get("DEPT_NAME"),?(Long)?m?
34?
35???????????????????????????????????????????.get("EMP_COUNT"));?
36?
37??????????????????????}?
38??????????????????????if?("PIE".equals(type))?{?
39?????????????????????????????chart?=?ChartFactory.createPieChart("PieChart",?data,?false,?
40?
41???????????????????????????????????????????false,?false);?
42??????????????????????}?else?{?
43?????????????????????????????chart?=?ChartFactory.createPieChart3D("PieChart3D",?data,?
44?
45???????????????????????????????????????????false,?false,?false);?
46??????????????????????}?
47???????????????}?else?{?
48??????????????????????DefaultCategoryDataset?data?=?new?DefaultCategoryDataset();?
49??????????????????????Iterator?it?=?list.iterator();?
50??????????????????????while?(it.hasNext())?{?
51?????????????????????????????Map?m?=?(Map)?it.next();?
52?????????????????????????????data.addValue((Long)?m.get("EMP_COUNT"),?"Department",?
53?
54???????????????????????????????????????????(String)?m.get("DEPT_NAME"));?
55??????????????????????}?
56?
57??????????????????????if?("BAR".equals(type))?{?
58?????????????????????????????chart?=?ChartFactory.createBarChart("BarChart",?"Department",?"Employee",?
59?
60???????????????????????????????????????????data,?PlotOrientation.VERTICAL,?false,?false,?false);?
61??????????????????????}?else?{?
62?????????????????????????????chart?=?ChartFactory.createBarChart3D("BarChart3D",?"Department",?
63?
64???????????????????????????????????????????"Employee",?data,?PlotOrientation.VERTICAL,?false,?false,?
65?
66???????????????????????????????????????????false);?
67??????????????????????}?
68???????????????}?
69???????????????return?chart;?
70????????}?
71?
72?}?
73?
74?
其中會用到Service層中新增加的接口List list = empService.getEmployeeCounts();
提示這個方法不存在，利用
Eclipse
的
Ctrl+1
功能
,
逐層添加
service -> serviceimpl -> dao - > daoimpl,
即快速又不易出錯。
?
值得注意的是：
第33行
,
這里要強制轉換成
Long
型，因為
iBATIS
中
count( )
函數的返回值為
Long
類型
.
?
如果要在
Servlet
中使用
Spring
提供的
Bean
配置文件，需要用到
WebApplicationContextUtils
，不過先要在
web.xml
中添加一個
Listener
才可以使用。
???
<context-param>
??????
<param-name>
contextConfigLocation
</param-name>
??????
<param-value>
?????????? classpath:spring.xml
</param-value>
???
</context-param>
???
<listener>
??????
<listener-class>
???
??? org.springframework.web.context.ContextLoaderListener
</listener-class>
???
</listener>
?
最后一步是在
iBATIS
的
Mapping
文件中加入
SQL
語句。。。。。。。
???
<select
id=
"getEmployeeCounts"
resultClass=
"java.util.HashMap"
cacheModel=
"employeesCache"
>
??????? SELECT
??????? d.name as DEPT_NAME,
?????? count(e.id) as EMP_COUNT
??????? FROM employee e, department d
??????? WHERE e.dept_id = d.id
?????? GROUP BY d.name
???
</select>
?
通過兩次
DEMO
，發現
iBATIS
算是不錯的東東，
配置比
Hibernate
簡單，使用上又比
JDBC
簡單。