这里我以id属性为例,从表中取到(任意)对象集合后,我想将其中的某一属性全部取出。
下面是利用反射的代码实现
@org.junit.Test
public void classTest(){
TbUser tbUser1 = new TbUser();
tbUser1.setId(new Long(12));
// EntityWrapper<TbUser> ew = new EntityWrapper<TbUser>();
// ew.ge("id",7);
// List<TbUser> tbUserList = tbUserMapper.selectList(ew);
// tbUserList.forEach(x ->{
// System.out.println(x.getUsername());
// } );
List<TbUser> tbUserList = tbUserMapper.selectPage(new Page<TbUser>(1, 10),new EntityWrapper<TbUser>());
List<String> IdList = getIdList(tbUserList);
System.out.println(IdList.size());
for (String s : IdList){
System.out.println(s);
}
}
private <T> List<String> getIdList(List<T> tList){
List<String> idList = new ArrayList<>();
for (T t : tList){
try {
idList.add(t.getClass().getMethod("getId").invoke(t).toString());
} catch (NoSuchMethodException e) {
e.printStackTrace();
}catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
return idList;
}
这里我是将取id写死了,当然也可以做一些修改以扩展其适用范围
另附lamda表达式写法(这里需要注意,子类的私有属性在这应该不合适)
public void classTest(){
TbUser tbUser1 = new TbUser();
tbUser1.setId(new Long(12));
// EntityWrapper<TbUser> ew = new EntityWrapper<TbUser>();
// ew.ge("id",7);
// List<TbUser> tbUserList = tbUserMapper.selectList(ew);
// tbUserList.forEach(x ->{
// System.out.println(x.getUsername());
// } );
List<TbUser> tbUserList = tbUserMapper.selectPage(new Page<TbUser>(1, 10),new EntityWrapper<TbUser>());
// List<String> IdList = getIdList(tbUserList);
List<Long> IdList = getIdList1(tbUserList);
System.out.println(IdList.size());
for (Long s : IdList){
System.out.println(s);
}
}
/**
* Lamda 表达式test
*/
public static List<Long> getIdList1(List<? extends BaseEntity> tList){
return tList.stream().map(BaseEntity :: getId).collect(Collectors.toList());
}
public class BaseEntity<T extends BaseEntity<T>> implements Serializable {
private static final Long serialVersionUID = 1L;
private Long id;
public static Long getSerialVersionUID() {
return serialVersionUID;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
}
这里我又做了些修改,支持同时访问父类和子类属性,如果有多继承的话,还需要再修改
private <T> List<?> getIdList(List<T> tList,String field,Boolean isSuperfield){
if(org.apache.commons.lang.StringUtils.isBlank(field))
return null;
//拼接方法
field = new StringBuffer("get").append(field.substring(0,1).toUpperCase()).append(field.substring(1)).toString();
List<Object> idList = new ArrayList<>();
Method method = null;
try {
if (isSuperfield)
method = tList.get(0).getClass().getSuperclass().getMethod(field);
else {
method = tList.get(0).getClass().getMethod(field);
}
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
try {
for (T t : tList){
Object s = method.invoke(t);
idList.add(s);
}
}catch (NullPointerException e){
e.printStackTrace();
}catch (InvocationTargetException e){
e.printStackTrace();
}catch (IllegalAccessException e){
e.printStackTrace();
}
return idList;
}
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