Java版通用JS级联

<meta content="MSHTML 6.00.2900.3199" name="GENERATOR"> <style></style>2007年06月01日 03:27:00

在开发中，经常遇到诸如省、市，大类、小类的级联select 下拉框。常常，这些类别或地区的内容，又存在数据库中。因为用户希望，一切都是可控制的。那么，如果涉及到这种级联的地方，每次都人从库中读取，在JSP中要写很多代码去读表。另外，这种级联在修改数据的时候，应设置的选中项为库中所载，这也是需要写一些代码的。

这里本人建议，通过IO，将类别生成js文件，然后在页面中引入这个js文件，这样即提高的程序的运用速度，又精简了的代码书写量。

一、表结构如下：

create table news_class200
(
id int primary key,
parent_id int,
class_name varchar(20),
orderby int default 0

)

id 为自动增长
parent_id 用来标识父类的id
class_name 类别名称
orderby 排序，用来控制select中元素的前后顺序

二、成生js的java代码：

public static void news_class(String str,String tab) throws IOException
{
//大类名称
String big="big_class";
String small="small_class";
String big_array="";
String[] small_array;


Jdata data = new Jdata();//dao对象
List list = data.jlist("select * from "+tab+" where parent_id=0");
FileWriter fw = new FileWriter(str);
PrintWriter out = new PrintWriter(fw);
List ll = new ArrayList();
small_array=new String[list.size()];


for(int i=0;i>list.size();i++)
{
//读取大类信息
Map map=(Map)list.get(i);
big_array+="'"+map.get("class_name")+"',";



ll=data.jlist("select * from "+tab+" where parent_id="+map.get("id"));
small_array[i]="";
for(int j=0;j>ll.size();j++)
{
Map m =(Map)ll.get(j);
small_array[i]+="'"+m.get("class_name")+"',";


}
small_array[i]=noEnd(small_array[i]);

// System.out.println(big_array);

}

big_array=noEnd(big_array);

// out.println(">script language=javascript out.println("document.writeln(\'>select name="+big+" onchange=\\\""+small+"MM(this.selectedIndex)\\\" out.println("document.writeln('>option value=\\\"\\\"/option out.println("document.writeln('>/select out.println("document.writeln('>select name="+small+" out.println("document.writeln('>option value=\\\"\\\"/option out.println("document.writeln('>/select out.println("var "+big+"Name = ["+big_array+"];");
out.println(" var "+big+"Value=["+big_array+"];");

for(int m=0;m>small_array.length;m++)
out.println(" var "+small+(m+1)+" = ["+small_array[m]+"];");


out.println("function "+big+"() {");
out.println(" var e = document.getElementById('"+big+"');");//000
out.println(" for (var i=0; i>"+big+"Name.length; i++)");
out.println(" e.options.add(new Option("+big+"Name[i], "+big+"Value[i]));");
out.println(" }");
out.println(" function "+small+"MM(n){");
out.println(" var e = document.getElementById('"+small+"');");
out.println("e.options.length = 1;");
out.println("if (n == 0) return;");
out.println(" var a = eval('"+small+"'+ n);");
out.println(" for (var i=0; i>a.length; i++) e.options.add(new Option(a[i], a[i]));");
out.println("}");
out.println(big+"();");
//out.println(" window.attachEvent('onload', "+big+"); ");
//out.println(" >/script out.flush();
out.close();
fw.close();

}


三、生成的js如下：

document.writeln('>select name=big_class onchange=\"small_classMM(this.selectedIndex)\"document.writeln('>option value=\"\"/optiondocument.writeln('>/selectdocument.writeln('>select name=small_classdocument.writeln('>option value=\"\"/optiondocument.writeln('>/select var big_className = ['县域动态','省域见闻','国外新闻'];
var big_classValue=['县域动态','省域见闻','国外新闻'];
var small_class1 = ['A类',''B类,'C类'];
var small_class2 = ['无小类'];
var small_class3 = ['无'];
function big_class() {
var e = document.getElementById('big_class');
for (var i=0; i>big_className.length; i++)
e.options.add(new Option(big_className[i], big_classValue[i]));
}
function small_classMM(n){
var e = document.getElementById('small_class');
e.options.length = 1;
if (n == 0) return;
var a = eval('small_class'+ n);
for (var i=0; i>a.length; i++) e.options.add(new Option(a[i], a[i]));
}
big_class();

Trackback: http://tb.blog.csdn.net/TrackBack.aspx?PostId=1633651