SpelEvaluationException：EL1007E:（pos 43）：在null上找不到字段或属性“group”

Question

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POJO摘要

// User Class
public class User {
    int id;
    String name;
    // getters and setters
}

// Group Class
public class Group {
    int id;
    String name;
    // getters and setters
}

// GroupMembership class
public class GroupMembership {
    private int id;
    private User user;
    private Group group;
    // getters and setters
}

对方法预授权筛选器。

@PreAuthorize("canIEditGroupProfile(#membership.group.id)")
public int updateGroupMembership(GroupMembership membership)
    throws GroupsServiceException;

在传递完全填充的groupmembership对象（存在正确的用户和组组合）时，安全筛选器引发以下异常：

errorMessage: "Failed to evaluate expression
    canIEditGroupProfile(#membership.group.id)'"

原因是：

org.springframework.expression.spel.SpelEvaluationException:
    EL1007E:(pos 33): Field or property 'group' cannot be found on null

请提供地址相同的指针。

Answer 1

getter/setter似乎很好...也没有null的情况。

然而这是一个有趣的观察；这条给了我一个错误：

@PreAuthorize("canIEditGroupProfile(#membership.group.id)")
public int updateGroupMembership(GroupMembership membership)
    throws GroupsServiceException; 

这很管用：

@PreAuthorize("canIEditGroupProfile(#groupmembership.group.id)")
public int updateGroupMembership(GroupMembership groupmembership)
    throws GroupsServiceException;