java - 如何使用流将 java bean 列表转换为另一个 bean 列表

Question

我有如下的 bean

public class CleanPermission {

    private int id;

    private int objectId;

    private boolean visible;
    private boolean order;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getObjectId() {
        return objectId;
    }

    public void setObjectId(int objectId) {
        this.objectId = objectId;
    }

    public boolean isVisible() {
        return visible;
    }

    public void setVisible(boolean visible) {
        this.visible = visible;
    }

    public boolean isOrder() {
        return order;
    }

    public void setOrder(boolean order) {
        this.order = order;
    }

}

public class Permission {

    private int id;

    private AppPermission appPermission;

    private int objectId;

    private boolean enabled;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public AppPermission getAppPermission() {
        return appPermission;
    }

    public void setAppPermission(AppPermission appPermission) {
        this.appPermission = appPermission;
    }

    public int getObjectId() {
        return objectId;
    }

    public void setObjectId(int objectId) {
        this.objectId = objectId;
    }

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

}

在CleanPermission.java中可见，顺序是指Permission.java中的AppPermission的权限

我将从服务器获取 CleanPermission 列表(列表)。我想根据权限类型将 CleanPermissions 列表转换为列表(可见创建单独的 Permission 对象)。

目前我正在进行如下转换。但我想使用 java 流来转换它。因此，我需要帮助来使用 java 流进行转换。

public List<Permission> get(List<CleanPermission> cleanPermissions) {
    List<Permission> permissions = new ArrayList();
    Permission permission;
    for (CleanPermission cleanPermission : cleanPermissions) {
        permission = new Permission();
        permission.setAppObjectType(cleanPermission.getAppObjectType());
        permission.setEnabled(cleanPermission.isVisible());
        permission.setAppPermission(new Permission(){{
            setId(1);
        }});
        permissions.add(permission);
        permission = new Permission();
        permission.setObjectId(cleanPermission.getObjectId());
        permission.setEnabled(cleanPermission.isOrder());
        permission.setAppPermission(new Permission(){{
            setId(2);
        }});
        permissions.add(permission);
    }
    if (!permissions.isEmpty()) {
        System.out.println(permissions.size());
    }
    return permissions;

}

示例数据:

List<CleanPermission> cleanPermissions = new ArrayList() {
    {
        add(new CleanPermission() {
            {
                setVisible(true);
                setOrder(false);
                setObjectId(1);
            }
        });
        add(new CleanPermission() {
            {
                setVisible(false);
                setOrder(false);
                setObjectId(2);
            }
        });
        add(new CleanPermission() {
            {
                setVisible(true);
                setOrder(true);
                setObjectId(3);
            }
        });                
    }
};

Answer 1

有很多种方法可以使用流 API 来重构它。首先我建议封装转换方法。

public List<Permission> convert(CleanPermission cp) {
    List<Permission> permissions= new ArrayList<>()
    permission = new Permission();
    permission.setAppObjectType(cleanPermission.getAppObjectType());
    permission.setEnabled(cleanPermission.isVisible());
    permission.setAppPermission(new Permission(){{
        setId(1);
    }});
    permissions.add(permission);
    permission = new Permission();
    permission.setObjectId(cleanPermission.getObjectId());
    permission.setEnabled(cleanPermission.isOrder());
    permission.setAppPermission(new Permission(){{
        setId(2);
    }});
    permissions.add(permission);
    return permissions;
}

以及处理

cleanPermissions.stream().map(this::convert)
     .flatMap(Collection::stream).collect(Collectors.toList());

或

cleanPermissions.stream().map(this::convert)
     .collect(ArrayList::new, ArrayList::addAll, ArrayList::addAll);