jqGrid与Struts2的结合应用（七） —— 浅谈排序

终于讲到排序了，这一部分应该说还是比较好理解的。

jqGrid通过colModel选项中的sortable来控制是否可以以某列的值排序。sortable的默认值是true，当设为false时，即此列不能用于排序。

[javascript]
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$(function(){
$("#gridTable").jqGrid({

...

colModel: [
{name:"id",index:"id",label:"编码",width:40},
{name:"lastName",index:"lastName",label:"姓",width:80},
{name:"firstName",index:"firstName",label:"名",width:80},
{name:"email",index:"email",label:"电子邮箱",width:160,sortable:false},
{name:"telNo",index:"telNo",label:"电话",width:120,sortable:false}
],

...

});
});

[java]
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package cn.gengv.struts2ex.jqGrid;
import java.text.Collator;
import java.util.Comparator;
import com.byzl.hare.model.Contact;
public class ContactComparatorFactory {
private static Collator collator_Chinese = Collator.getInstance(java.util.Locale.CHINA);
private final static Comparator<Contact> idComparator = new IdComparator();
private final static Comparator<Contact> firstNameComparator = new FirstNameComparator();
private final static Comparator<Contact> lastNameComparator = new LastNameComparator();
private final static Comparator<Contact> fullNameComparator = new FullNameComparator();
private final static Comparator<Contact> idCardNoNoComparator = new IdCardNoComparator();
private final static Comparator<Contact> nationalityComparator = new NationalityComparator();

public static Comparator<Contact> getComparator(String compareType) {
if ("id".equalsIgnoreCase(compareType)) {
return idComparator;
} else if ("firstName".equalsIgnoreCase(compareType)) {
return firstNameComparator;
} else if ("lastName".equalsIgnoreCase(compareType)) {
return lastNameComparator;
} else if ("fullName".equalsIgnoreCase(compareType)) {
return fullNameComparator;
} else if ("idCardNoNo".equalsIgnoreCase(compareType)) {
return idCardNoNoComparator;
} else if ("nationality".equalsIgnoreCase(compareType)) {
return nationalityComparator;
} else {
return null;
}
}

public static class IdComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
int id1 = c1.getId();
int id2 = c2.getId();
return id1 == id2 ? 0 : (id1 < id2 ? -1 : 1);
}
}
}

public static class FirstNameComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getFirstName();
String s2 = c2.getFirstName();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return collator_Chinese.compare(s1, s2);
}
}
}
}

public static class LastNameComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getLastName();
String s2 = c2.getLastName();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return collator_Chinese.compare(s1, s2);
}
}
}
}

public static class FullNameComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getFullName();
String s2 = c2.getFullName();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return collator_Chinese.compare(s1, s2);
}
}
}
}

public static class IdCardNoComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getIdCardNo();
String s2 = c2.getIdCardNo();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return s1.compareToIgnoreCase(s2);
}
}
}
}

public static class NationalityComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getNationality();
String s2 = c2.getNationality();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return collator_Chinese.compare(s1, s2);
}
}
}
}

}

package cn.gengv.struts2ex.jqGrid;
import java.text.Collator;
import java.util.Comparator;
import com.byzl.hare.model.Contact;
public class ContactComparatorFactory {
private static Collator collator_Chinese = Collator.getInstance(java.util.Locale.CHINA);
private final static Comparator<Contact> idComparator = new IdComparator();
private final static Comparator<Contact> firstNameComparator = new FirstNameComparator();
private final static Comparator<Contact> lastNameComparator = new LastNameComparator();
private final static Comparator<Contact> fullNameComparator = new FullNameComparator();
private final static Comparator<Contact> idCardNoNoComparator = new IdCardNoComparator();
private final static Comparator<Contact> nationalityComparator = new NationalityComparator();

public static Comparator<Contact> getComparator(String compareType) {
if ("id".equalsIgnoreCase(compareType)) {
return idComparator;
} else if ("firstName".equalsIgnoreCase(compareType)) {
return firstNameComparator;
} else if ("lastName".equalsIgnoreCase(compareType)) {
return lastNameComparator;
} else if ("fullName".equalsIgnoreCase(compareType)) {
return fullNameComparator;
} else if ("idCardNoNo".equalsIgnoreCase(compareType)) {
return idCardNoNoComparator;
} else if ("nationality".equalsIgnoreCase(compareType)) {
return nationalityComparator;
} else {
return null;
}
}

public static class IdComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
int id1 = c1.getId();
int id2 = c2.getId();
return id1 == id2 ? 0 : (id1 < id2 ? -1 : 1);
}
}
}

public static class FirstNameComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getFirstName();
String s2 = c2.getFirstName();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return collator_Chinese.compare(s1, s2);
}
}
}
}

public static class LastNameComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getLastName();
String s2 = c2.getLastName();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return collator_Chinese.compare(s1, s2);
}
}
}
}

public static class FullNameComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getFullName();
String s2 = c2.getFullName();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return collator_Chinese.compare(s1, s2);
}
}
}
}

public static class IdCardNoComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getIdCardNo();
String s2 = c2.getIdCardNo();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return s1.compareToIgnoreCase(s2);
}
}
}
}

public static class NationalityComparator implements Comparator<Contact> {
public int compare(Contact c1, Contact c2) {
if (c1 == null && c2 == null) {
return 0;
} else if (c1 == null && c2 != null) {
return -1;
} else if (c1 != null && c2 == null) {
return 1;
} else {
String s1 = c1.getNationality();
String s2 = c2.getNationality();

if (s1 == null && s2 == null) {
return 0;
} else if (s1 == null && s2 != null) {
return -1;
} else if (s1 != null && s2 == null) {
return 1;
} else {
return collator_Chinese.compare(s1, s2);
}
}
}
}

}

然后再来看JqGridBaseAction，其中添加了一个抽象方法，用来将数据结果进行排序。

[java]
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package cn.gengv.struts2ex.jqGrid;

// import ...

@SuppressWarnings("serial")
public abstract class JqGridBaseAction<T> extends ActionSupport {
...

// (1)添加排序方法
public abstract void sortResults(List<T> results, String field, String order);

public String refreshGridModel() {
try {
List<Criterion> criteria = Collections.emptyList();

if(search == true) {
criteria = new ArrayList<Criterion>();

if(filters != null && filters.length()>0) {
criteria.addAll(this.generateSearchCriteriaFromFilters(filters));
}

Criterion criterion = this.generateSearchCriterion(searchField, searchString, searchOper);
if(criterion != null) {
criteria.add(criterion);
}
}

List<T> results = Collections.emptyList();

int from = rows * (page - 1);
int length = rows;

if(loadonce) {
from = 0;
length = 100;
}

if(!criteria.isEmpty()) {
record = this.getResultSize(criteria);
results = this.listResults(criteria, from, length);

} else {
record = this.getResultSize();
results = this.listResults(from, length);

}

// (2)将结果排序
if(sidx != null && sord != null) {
sortResults(results, sidx, sord);
}

this.setGridModel(results);
total = (int) Math.ceil((double) record / (double) rows);
return SUCCESS;
} catch (Exception e) {
e.printStackTrace();
this.addActionError(e.getMessage());
return ERROR;
}
}

...
}

[java]
view plaincopyprint?

package cn.gengv.struts2ex.jqGrid;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import com.byzl.hare.dao.impl.Criterion;
import com.byzl.hare.model.Contact;
import com.byzl.hare.service.ContactService;

@SuppressWarnings("serial")
public class ListContactsAction extends JqGridBaseAction<Contact> {

...

@Override
public void sortResults(List<Contact> results, String field, String order) {
// (1)根据field获得对应的Comparator

Comparator<Contact> comparator = ContactComparatorFactory.getComparator(field);

if(comparator != null) {
// (2)使用Comparator排序

Collections.sort(results, comparator);

// (3)如果需要的排序顺序为desc，则颠倒顺序

if("desc".equals(order)) {
Collections.reverse(results);
}
}

}

...
}

package cn.gengv.struts2ex.jqGrid;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import com.byzl.hare.dao.impl.Criterion;
import com.byzl.hare.model.Contact;
import com.byzl.hare.service.ContactService;

@SuppressWarnings("serial")
public class ListContactsAction extends JqGridBaseAction<Contact> {

...

@Override
public void sortResults(List<Contact> results, String field, String order) {
// (1)根据field获得对应的Comparator
Comparator<Contact> comparator = ContactComparatorFactory.getComparator(field);

if(comparator != null) {
// (2)使用Comparator排序
Collections.sort(results, comparator);

// (3)如果需要的排序顺序为desc，则颠倒顺序
if("desc".equals(order)) {
Collections.reverse(results);
}
}

}

...
}

不过这个例子存在一定的局限性，即只能将当前页中的数据根据某列进行排序；而不能跨页间进行数据排序。之所以存在这种局限，也是源于实际应用中的客观限制。还以这个例子来说，数据库里总共模拟了两万多条数据记录。如果每次要将这些记录进行排里的话，除非有数据库索引支持，否则所要消耗的时间也是相当客观的，对于用户体验来说，几乎就是灾难。如果数据量更多的话，结果可想而知。

因此，我们应该换一个角度来看这个问题，用户之所以使用排序，更多的目的还是在于查找数据方便，既然我们可以提供条件查询（尤其是复杂条件查询），那么用户对于排序的需求也就不会那么迫切了。同时也可以体会到，排序更多地应用在少量数据的场合下。