java Spring 中的命令对象
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Command Objects in Spring
提问by Jeune
I have a command object composed of primitive fields and an object field. How do I bind my form fields to the fields in the object?
我有一个由原始字段和对象字段组成的命令对象。如何将表单字段绑定到对象中的字段？
I tried doing this but to no avail
我尝试这样做但无济于事
<form:form commandName="course" method="POST">
<form:input path="activity.activity"/>
.
.
.
</form:form>
I get this error
我收到这个错误
org.springframework.beans.NotReadablePropertyException:
Invalid property 'course' of bean class
My Command class is like this
我的命令类是这样的
public class Course {
private long id;
private String owner;
private String title;
private List<LearningActivity> activity = new ArrayList<LearningActivity>();
//getters and setters
}
public class LearningActivity {
private long ID;
private String activity;
private String link;
//getters and setters
}
采纳答案by Jacob Mattison
Your list either needs to be pre-populated with as many LearningActivity objects as you plan to refer to (using activity[0], activity[1], etc.) or it needs to be a lazy list. A lazy list is a list that will populate itself with empty objects when a given index is referenced.
您的列表要么需要预先填充您计划引用的尽可能多的 LearningActivity 对象（使用活动 [0]、活动 [1] 等），要么需要是一个惰性列表。惰性列表是一个列表，当引用给定索引时，它将用空对象填充自身。
A comment indicates that you're trying to use Apache Commons LazyList, which ought to work -- are you missing an import directive? However, as an alternative there is a Spring lazy list implementation called AutoPopulatingList.
一条评论表明您正在尝试使用 Apache Commons LazyList，它应该可以工作——您是否缺少导入指令？但是，作为替代方案，有一个名为 AutoPopulatingList 的 Spring 惰性列表实现。
回答by ChssPly76
Two possible issues here:
这里有两个可能的问题：
activity.activityis invalid (unless your getters do not correspond to your member variables) becauseCourse.activityis a list. You need to address a particular list element - e.g.activity[0].activity. You'll also have to make sure it actually exists.Have you configured your FormController correctly? Does it pass
Courseinstance to view as it should? Take a look at Spring MVC tutorialfor an example.
activity.activity无效（除非您的 getter 与您的成员变量不对应），因为Course.activity是一个列表。您需要解决特定的列表元素 - 例如activity[0].activity。您还必须确保它确实存在。您是否正确配置了 FormController？它是否通过
Course实例进行查看？以Spring MVC 教程为例。
If after you've fixed #1 and verified that #2 is done correctly the error doesn't go away, please post more details (FormController mapping / source).
如果在您修复 #1 并验证 #2 正确完成后，错误没有消失，请发布更多详细信息（FormController 映射/源代码）。
