Java反射：将List对象集合转为ListMap集合/MapList集合形式

https://blog.csdn.net/qq_36937684/article/details/116725780

今天使用SpringBoot导入common-beanutils运行的时候总是报NoClassDefFoundError: XXX，所以决定自己写一个类实现 将对象List集合转为以下两种形式：
List<T> --> List<Map<String, Object>>， List<T> --> Map<String, List<Object>>

代码
/**
* 基于反射，将obj转为map
*/
public class BeanUtil {
/**
* Pojo -> Map<String, Object>
* @param obj
* @return
* @throws Exception
*/
public static Map<String,Object> object2Map(Object obj) throws Exception{
Map<String,Object> map = new HashMap<String, Object>();
Field[] fields = obj.getClass().getDeclaredFields();
for(Field field:fields){
field.setAccessible(true);
map.put(field.getName(), field.get(obj));
}
return map;
}

/**
* List<T> --> List<Map<String, Object>>
* @param objectList
* @param <T>
* @return
* @throws Exception
*/
public static <T> List<Map<String, Object>> objectList2ListMap(List<T> objectList) throws Exception {
ArrayList<Map<String, Object>> resultList = new ArrayList<>();
Map<String, Object> map = new HashMap<>();
for (T t : objectList) {
resultList.add(object2Map(t));
}
return resultList;
}

/**
* List<T> --> Map<String, List<Object>>
* @param objectList
* @param keyName
* @param <T>
* @return
* @throws Exception
*/
public static <T> Map<String, List<Object>> objectList2MapList(List<T> objectList, String[] keyName) throws Exception{
Map<String, List<Object>> resultMap = new HashMap<>();
for(int i = 0; i < keyName.length; i++){
List<Object> arrayList = new ArrayList<>();
for (T t: objectList){// List有序，所以对每个对象依次变为map,然后得到对应的值，存入arrayList
arrayList.add(object2Map(t).get(keyName[i]));
}
resultMap.put(keyName[i], arrayList);//将keyName和对应List集合存入resultMap
}
return resultMap;
}
}

测试
测试的时候传入的是List<Statistics>类型，以及对应的pojo:

@Data
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class Statistics {
private String className;
private Double maxScore;
private Double minScore;
private Double avgScore;
private Integer countStudent;// 学生人数

}

@SpringBootTest(classes = ShizuoApplication.class)
@RunWith(SpringRunner.class)
public class StudentTest {

@Autowired
StudentService studentService;
@Test
public void test() throws Exception {
System.out.println(studentService);
List<Statistics> statistics = studentService.statistics();
List<Map<String, Object>> maps = BeanUtil.objectList2ListMap(statistics);
System.out.println(maps);

Map<String, List<Object>> map = BeanUtil.objectList2MapList(statistics, new String[]{"minScore","maxScore","avgScore","countStudent","className"});
System.out.println(map);

indi.huishi.shizuo.service.impl.StudentServiceImpl@8f0007
[{minScore=76.2, avgScore=83.5333, countStudent=6, className=1, maxScore=88.0}, {minScore=80.0, avgScore=83.3, countStudent=5, className=2, maxScore=86.0}, {minScore=59.0, avgScore=72.84, countStudent=5, className=3, maxScore=85.2}, {minScore=64.0, avgScore=64.0, countStudent=1, className=5, maxScore=64.0}]
{minScore=[76.2, 80.0, 59.0, 64.0], avgScore=[83.5333, 83.3, 72.84, 64.0], countStudent=[6, 5, 5, 1], className=[1, 2, 3, 5], maxScore=[88.0, 86.0, 85.2, 64.0]}

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原文链接：https://blog.csdn.net/qq_36937684/article/details/116725780