关于对List的通用排序实现

List的排序大家都会想到实现Comparator接口，但是如果我们需要对list排序是动态，就比较崩溃了，复杂度不言而喻。经过仔细思索，写了一个工具类，使用反射机制实现对list对象的排序功能，专门用于List对象的排序工作。

package xzknet.net.csdn.blog.utils;import java.beans.PropertyDescriptor;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.util.Collections;import java.util.Comparator;import java.util.HashMap;import java.util.LinkedHashMap;import java.util.List;import java.util.Map;import org.springframework.beans.BeanUtils;/** * List排序工具 *  * @author Ken.xu(mailto:[e-mail]) * @version 1.0 Copyright 2012-9-18 下午04:37:17 * @param <T> */public class ListSortUtil<T> {private Map<Method, Direction> sortField = new LinkedHashMap<Method, Direction>();private Map<String, Method> propertyMethodMap = null;// Method[] methodspublic ListSortUtil(final Class clazz) {PropertyDescriptor[] propertyDescriptor = BeanUtils.getPropertyDescriptors(clazz);Map<String, Method> propertyMethodMap = new HashMap<String, Method>();for (PropertyDescriptor pd : propertyDescriptor) {String key = pd.getName();Method value = pd.getReadMethod();propertyMethodMap.put(key, value);}this.propertyMethodMap = propertyMethodMap;}public void clear() {sortField.clear();}/** * 增加一个降序 *  * @param fieldName * @throws NoSuchMethodException * @author Ken_xu */public void addDesc(String fieldName) throws NoSuchMethodException {addFieldMethod(fieldName, Direction.DESC);}/** * 增加一个升序 *  * @param fieldName * @throws NoSuchMethodException * @author Ken_xu */public void addAsc(String fieldName) throws NoSuchMethodException {addFieldMethod(fieldName, Direction.ASC);}/** * 增加一个字段排序模式 *  * @param fieldName * @param direction * @throws NoSuchMethodException * @author Ken_xu */private void addFieldMethod(String fieldName, Direction direction) throws NoSuchMethodException {Method method = propertyMethodMap.get(fieldName);if (method == null) {throw new NoSuchMethodException(fieldName);} else {sortField.put(method, direction);}}public List<T> sortList(List<T> list) {if (sortField.isEmpty() == false) {Comparator<T> comparator = new Comparator<T>() {public int compare(T o1, T o2) {int flag = 0;for (Map.Entry<Method, Direction> entry : sortField.entrySet()) {Method method = entry.getKey();Direction direction = entry.getValue();if (direction == Direction.ASC) {// DESC:降序flag = this.compareByFlag(method, o1, o2);} else {// ASC:升序flag = this.compareByFlag(method, o2, o1);}if (flag != 0) {break;}}if (flag > 0) {flag = 1;} else if (flag < 0) {flag = -1;}return flag;}/** * 如果t1大于t2:1<br> * t1等于t2:0<br> * t1小于t2:-1 *  * @param flag * @param t1 * @param t2 * @return * @author Ken_xu */private int compareByFlag(Method method, T t1, T t2) {int flag = 0;try {String methodReturn1 = method.invoke(t1).toString();String methodReturn2 = method.invoke(t2).toString();flag = methodReturn1.compareTo(methodReturn2);} catch (IllegalArgumentException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();}return flag;}};Collections.sort(list, comparator);}return list;}/** * 排序方式： * <p> * ASC:升序<br/> DESC:降序 *  */enum Direction {ASC, DESC};}

测试用例也给大家提供一个

package xzknet.net.csdn.blog.utils;import java.util.ArrayList;import java.util.List;import junit.framework.TestCase;public class ListSortUtilTest extends TestCase {private List<TestUser> list = null;/** * 打印清单 *  * @author Ken_xu */private void printListEg() {List<TestUser> TestUserList = new ArrayList<TestUser>();for (int i = 0, maxIdx = list.size(); i < maxIdx; i++) {TestUser tm = list.get(i);String showTxt = String.format("%d)\t modelName=%s;\t\t extendsModel=%s;", i, tm.getModelName(), tm.getExtendsModels());System.out.println(showTxt);if (i == (maxIdx - 1)) {showTxt = String.format("...................总共：%d条", list.size());System.out.println(showTxt);}TestUserList.add(tm);}list = TestUserList;}/** * 初始化测试用例 */protected void setUp() throws Exception {super.setUp();List<TestUser> TestUserList = new ArrayList<TestUser>();long rowNum = 0l;for (int i = 0; i < 10; i++) {TestUser tm = new TestUser();if (i % 2 == 0) {// 每两个对象的modelName相同rowNum = Math.round(Math.random() * 100);}tm.setModelName("AAA_TEST_" + rowNum);tm.setExtendsModels("BBBBBBB" + i);TestUserList.add(tm);}list = TestUserList;}/** * 测试排序 *  * @author Ken_xu */public void testSort() {ListSortUtil<TestUser> sortUtil = new ListSortUtil(TestUser.class);try {sortUtil.addDesc("modelName");sortUtil.addAsc("extendsModels");} catch (NoSuchMethodException e) {e.printStackTrace();}System.out.println("打印排序前结果");printListEg();sortUtil.sortList(list);System.out.println("打印排序后结果");printListEg();}class TestUser {String modelName, extendsModels;public String getModelName() {return modelName;}public void setModelName(String modelName) {this.modelName = modelName;}public String getExtendsModels() {return extendsModels;}public void setExtendsModels(String extendsModels) {this.extendsModels = extendsModels;}}}

 

测试结果如下：

打印排序前结果0) modelName=AAA_TEST_48; extendsModel=BBBBBBB0;1) modelName=AAA_TEST_48; extendsModel=BBBBBBB1;2) modelName=AAA_TEST_29; extendsModel=BBBBBBB2;3) modelName=AAA_TEST_29; extendsModel=BBBBBBB3;4) modelName=AAA_TEST_1; extendsModel=BBBBBBB4;5) modelName=AAA_TEST_1; extendsModel=BBBBBBB5;6) modelName=AAA_TEST_63; extendsModel=BBBBBBB6;7) modelName=AAA_TEST_63; extendsModel=BBBBBBB7;8) modelName=AAA_TEST_73; extendsModel=BBBBBBB8;9) modelName=AAA_TEST_73; extendsModel=BBBBBBB9;...................总共：10条打印排序后结果0) modelName=AAA_TEST_73; extendsModel=BBBBBBB8;1) modelName=AAA_TEST_73; extendsModel=BBBBBBB9;2) modelName=AAA_TEST_63; extendsModel=BBBBBBB6;3) modelName=AAA_TEST_63; extendsModel=BBBBBBB7;4) modelName=AAA_TEST_48; extendsModel=BBBBBBB0;5) modelName=AAA_TEST_48; extendsModel=BBBBBBB1;6) modelName=AAA_TEST_29; extendsModel=BBBBBBB2;7) modelName=AAA_TEST_29; extendsModel=BBBBBBB3;8) modelName=AAA_TEST_1; extendsModel=BBBBBBB4;9) modelName=AAA_TEST_1; extendsModel=BBBBBBB5;...................总共：10条