我的DTO如下
public class UserDTO implements Serializable {
private String id;
private String fullName;
private String phone;
private String role;
private List<String> roleList;
public UserDTO(String id, List<String> roleList) {
super();
this.id = id;
this.roleList = roleList;
}
}
我有以下清单 UserDTO
哪儿 roleList
没有人烟,但 role
是填充的。问题是 role
可以是多个,但不知何故,我无法在一个查询中获得列表。所以,我想按id分组,然后生成 roleList
.
例如,我有以下几行。
id fullName phone role roleList
------------------------------------------------
abc Sarwar 017xxx admin NULL
abc Sarwar 017xxx operator NULL
I want it to be like the following
abc Sarwar 017xxx NULL ArrayList<String>(admin, operator)
我试过下面的方法,但没有用(不应该,但我不知道应该怎么做) 这就是为什么我寻求你的帮助。
Map<String, List<UserDTO>> resultsWithSameIdAndName = users.stream()
.collect(Collectors.groupingBy(r -> r.getId()));
List<UserDTO> mergedResults = resultsWithSameIdAndName.entrySet().stream()
.map(e -> new UserDTO(e.getKey(),
e.getValue().stream().map(r -> r.getRole()).collect(Collectors.toList())))
.collect(Collectors.toList());
先谢谢你
你的代码应该能用。我又加了一个方法。
首先准备地图 roleList
用户 id
Map<String, List<String>> resultsWithSameIdAndName = users.stream()
.collect(Collectors.groupingBy(UserDTO::getId,
Collectors.mapping(d-> d.getRole(), Collectors.toList())));
然后按用户创建唯一的用户列表 id
List<UserDTO> uniqueUsers = users.stream()
.collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(UserDTO::getId))),ArrayList::new));
并从地图中获取角色列表,并为每个用户设置
for(UserDTO user :uniqueUsers) {
user.setRoleList(resultsWithSameIdAndName.get(user.getId()));
}
这可能对你有用。
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class UserDTO {
private String id;
private String fullName;
private String phone;
private String role;
private List<String> roleList;
public UserDTO(String id,String fullName,String phone,String role) {
this.id = id;
this.fullName = fullName;
this.phone = phone;
this.role =role;
}
public UserDTO(UserDTO oldObject,String key, List<String> collect) {
this.id = key;
this.fullName = oldObject.getFullName();
this.phone = oldObject.getPhone();
this.roleList = collect;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getFullName() {
return fullName;
}
public void setFullName(String fullName) {
this.fullName = fullName;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getRole() {
return role;
}
public void setRole(String role) {
this.role = role;
}
public List<String> getRoleList() {
return roleList;
}
public void setRoleList(List<String> roleList) {
this.roleList = roleList;
}
public static void main(String[] args) {
ArrayList<UserDTO> list = new ArrayList<>();
list.add(new UserDTO("ASD", "John", "12345", "user"));
list.add(new UserDTO("ASD", "John", "12345", "admin"));
list.add(new UserDTO("SDB", "Smith", "12345", "super user"));
list.add(new UserDTO("SDB", "Smith", "12345", "admin"));
list.add(new UserDTO("DFG", "Neo", "12345", "user"));
Map<String, List<UserDTO>> resultsWithSameIdAndName = list.stream().collect(Collectors.groupingBy(UserDTO::getId));
List<UserDTO> mergedResults = resultsWithSameIdAndName.entrySet().stream()
.map(e -> new UserDTO(
e.getValue().get(0),
e.getKey(),
e.getValue().stream().map(UserDTO::getRole).collect(Collectors.toList())))
.collect(Collectors.toList());
System.out.println(mergedResults);
}
}
我所做的唯一改变是在构造函数中增加了一个参数,它需要一个... ... UserDTO
对象。