Java 如何在servlet jsp/jsp servlet中过滤arraylist结果?
你好,朋友,在我的项目中,我有一个arraylist,在jsp页面表中显示数据库给定内容的结果,我想在其中添加一个过滤器,只显示列表中匹配的内容Java 如何在servlet jsp/jsp servlet中过滤arraylist结果?,java,filter,arraylist,Java,Filter,Arraylist,你好,朋友,在我的项目中,我有一个arraylist,在jsp页面表中显示数据库给定内容的结果,我想在其中添加一个过滤器,只显示列表中匹配的内容 the table which is coming out is as: student_id class_id student_name 1x0001 10 Ashish 1x2001 11 Alex 1x2002 11 Atr. 1x0001 1
the table which is coming out is as:
student_id class_id student_name
1x0001 10 Ashish
1x2001 11 Alex
1x2002 11 Atr.
1x0001 10 Alok
.............going on...
但我希望结果只显示类_id::11的页面,并删除其他结果。如何做到这一点
List dataList = new ArrayList();
rs = s.getResultSet();
while (rs.next ()){
//Add records into data list
dataList.add(rs.getInt("class_id"));
dataList.add(rs.getString("name"));
dataList.add(rs.getString("student_id"));
}
然后通过获取arraylist在servlet中显示结果:
我想要的是将问题显示为一个过滤表,arraylist而不是DB为:
the table which is coming(result???) out on servlet is as:
student_id class_id student_name
1x2001 11 Alex
1x2002 11 Atr.
.............going on...
问题在哪里。像Adeel说的那样,在SQL查询中这样放置条件,
where class\u id=?
您应该在SQL层进行过滤
此外,您应该使用Bean/Class/Struct来保存每条记录,而不是将所有数据以非结构化方式堆积到单个ArrayList中
但是,以下代码会满足您的要求:
public class FilterTest {
public static int COLS_PER_RECORD = 3;
public static void main(String[] args) {
ArrayList dataList = populateTestData();
printRecords(dataList);
ArrayList filtered = filterForClassId(dataList, 2);
printRecords(filtered);
}
private static ArrayList populateTestData() {
ArrayList dataList = new ArrayList();
ResultSet rs = s.getResultSet();
while (rs.next()) {
dataList.add(rs.getInt("class_id"));
dataList.add(rs.getString("name"));
dataList.add(rs.getString("student_id"));
}
return dataList;
}
private static ArrayList filterForClassId(ArrayList dataList,
int classIdToFilterFor) {
ArrayList filtered = new ArrayList();
Integer classIdToFilterForInteger = new Integer(classIdToFilterFor);
for (int i = 0; i < dataList.size(); i += COLS_PER_RECORD) {
if (classIdToFilterForInteger.equals(dataList.get(i))) {
for (int j = 0; j < COLS_PER_RECORD; j++) {
filtered.add(dataList.get(i + j));
}
}
}
return filtered;
}
private static void printRecords(ArrayList dataList) {
System.out.println("----");
for (int i = 0; i < dataList.size(); i += COLS_PER_RECORD) {
System.out.println("class_id=" + dataList.get(i) + " name="
+ dataList.get(i + 1) + " student_id="
+ dataList.get(i + 2));
}
System.out.println("----");
}
}
公共类过滤器测试{
公共静态int COLS_PER_记录=3;
公共静态void main(字符串[]args){
ArrayList dataList=populateTestData();
打印记录(数据列表);
ArrayList filtered=filterForClassId(数据列表,2);
打印记录(过滤);
}
私有静态ArrayList populateTestData(){
ArrayList dataList=新的ArrayList();
ResultSet rs=s.getResultSet();
while(rs.next()){
dataList.add(rs.getInt(“class_id”);
add(rs.getString(“name”);
添加(rs.getString(“学生id”);
}
返回数据列表;
}
专用静态ArrayList筛选器ForClassID(ArrayList数据列表,
int classIdToFilterFor){
ArrayList filtered=新的ArrayList();
整数classIdToFilterForInteger=新整数(classIdToFilterFor);
for(int i=0;i