作者qrtt1 (愚人)
站內java
標題Re: 用servlet呈現 piechart 無法顯現在網頁中
時間Sun Nov 11 11:45:59 2007
看到一堆 jsp 就暈了 囧rz
---------------------------------------------------------------
String path2 = request.getRealPath(".");
try
{
File image = new File(path2 +"\\MyChart2.png");
ChartUtilities.saveChartAsPNG(image, chart, 640, 480);
}
catch (Exception exc)
{
}
out.println("<p><img src = 'MyChart2.png'></img></p>");
這樣寫有潛在的問題 src = 'MyChart2.png'
除非你確定你的 jsp 只會在 context root
不然應該要是
request.getContextPath() + '/' + 'MyChart2.png'
要以 context path 為起始點來算比較保險
如果用 jstl 就會寫成
<img src="<c:url value="/MyChar2.png" />" />
---------------------------------------------------------------
if(drawback.equals("1")){
where_condiction = " and (缺失態樣 like '%1%') ";
}
您 equals 的習慣不太好. 只要 drawback 不小心為 null 你的程式就掛在那邊
改成 "1".equals(fooooo) 比較好
---------------------------------------------------------------
if(tartype.equals("0")){
selcase = " where (預算金額 > 0 ) ";
temptype = "的所有稽核案件";
temptype2 = "所有稽核採購案件";
}
if(tartype.equals("1")){
selcase = " where (採購標的性質 = '工程' ) ";
temptype = "的工程稽核案件";
temptype2 = "工程類稽核採購案件";
}
if(tartype.equals("2")){
selcase = " where (採購標的性質 = '勞務' ) ";
temptype = "的勞務稽核案件";
temptype2 = "勞務類稽核採購案件";
}
if(tartype.equals("3")){
selcase = " where (採購標的性質 = '財物' ) ";
temptype = "的財物稽核案件";
temptype2 = "財物類稽核採購案件";
}
if(tartype.equals("4")){
}
IF 太長了, 蠻傷腦筋的
比較好維護的方式大概會寫成
public abstract class SelectType {
String selcase;
String temptype;
String temptype2;
public String getSelcase() {
return selcase;
}
public void setSelcase(String selcase) {
this.selcase = selcase;
}
public String getTemptype() {
return temptype;
}
public void setTemptype(String temptype) {
this.temptype = temptype;
}
public String getTemptype2() {
return temptype2;
}
public void setTemptype2(String temptype2) {
this.temptype2 = temptype2;
}
}
class AllType extends SelectType {
public AllType() {
selcase = " where (預算金額 > 0 ) ";
temptype = "的所有稽核案件";
temptype2 = "所有稽核採購案件";
}
}
class EngineeringType extends SelectType {
public EngineeringType() {
selcase = " where (採購標的性質 = '工程' ) ";
temptype = "的工程稽核案件";
temptype2 = "工程類稽核採購案件";
}
}
class ServiceType extends SelectType {
public ServiceType() {
selcase = " where (採購標的性質 = '勞務' ) ";
temptype = "的勞務稽核案件";
temptype2 = "勞務類稽核採購案件";
}
}
class EffectsType extends SelectType {
public EffectsType() {
selcase = " where (採購標的性質 = '財物' ) ";
temptype = "的財物稽核案件";
temptype2 = "財物類稽核採購案件";
}
}
====================================================================
if(tartype.equals("2")){
selcase = " where (採購標的性質 = '勞務' ) ";
temptype = "的勞務稽核案件";
temptype2 = "勞務類稽核採購案件";
}
把要用到的 SelectType 可以先放到 Map 裡
您就不需要 if... 來決定設定的值
map.get("2") 取得一個 ServiceType 的 instance
整串 if 變成一個 map get method 會比較不容易出錯
也方便加新的 type
===================================================================
而後面也有 where_condition 做法也可以模仿, 不過可能要迂迴一點的做法
像是建立一個 Decorator 類別
abstract class WhereConditionDecorator extends SelectType {
SelectType selectType;
public WhereConditionDecorator(SelectType selectType) {
this.selectType = selectType;
}
public abstract String getSelcase();
}
class WhereCondition_anyone extends WhereConditionDecorator {
public WhereCondition_anyone(SelectType selectType) {
super(selectType);
}
public String getSelcase() {
return selectType.getSelcase() + " " +
"and ((缺失態樣 like '%1%') " +
"or (缺失態樣 like '%2%') " +
"or (缺失態樣 like '%3%') " +
"or (缺失態樣 like '%4%') " +
"or (缺失態樣 like '%5%') " +
"or (缺失態樣 like '%6%') " +
"or (缺失態樣 like '%7%') " +
"or (缺失態樣 like '%8%') " +
"or (缺失態樣 like '%9%')) ";
}
}
有了他, 你可以利用已經取得的 SelectType 實體再建立一個新的物件
new WhereCondition_anyone(type).getSelcase()
您就算是透過物件的手法幫您產生 sql string
where (採購標的性質 = '勞務' ) and ((缺失態樣 like '%1%') or (缺失態樣 like
'%2%') or (缺失態樣 like '%3%') or (缺失態樣 like '%4%') or (缺失態樣 like
'%5%') or (缺失態樣 like '%6%') or (缺失態樣 like '%7%') or (缺失態樣 like
'%8%') or (缺失態樣 like '%9%'))
--
雖然講那麼多
不知對您現在的用處大不大
不過您可以留著以後有閒再來改看也說不定 :)
java 也能寫得很有趣 ^^
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1F：推 cklonger:獲益良多 11/11 13:32
2F：推 mybluesky:大推此文章，此文該M才是 11/15 00:39