Spring Roo不会为.aj文件中的字段添加FetchType.LAZY，我应该手动执行它吗？ [英] Spring Roo doesn't add FetchType.LAZY for fields in .aj files, Should I do it manually?
问题描述
这些是一个问题，如果Spring Roo通过反向工程为.aj文件中的Set字段添加FetchType.LAZY，或者我应该手动执行它？
如果FetchType.LAZY不存在于.aj文件中，我可以通过查询SELECT st1 FROM parentTable t1 JOIN FETCH t1.childTable st1进入select，对吗？
这里的要点是，我可以手动添加FetchType.LAZY到文件（重构.aj文件>推入..），然后在.java文件（如果我想让Roo将控件保留在我的域类上，则风险高） 。
关于通过查询来完成它，我无法做到这一点，因为我得到了：
>查询指定的连接提取，但获取的关联的所有者不在选择列表中[FromElement {显式，不是集合连接，访存连接，获取非惰性属性，classAlias = ii，role = ... domain.Industry .i18nIndustries，
tableName = .. I18nIndustry，
tableAlias = i18nindust3_，
origin = ..行业industry2_，
列= {industry2_.IdIndustry，className = .. domain.I18nIndustry }}]
[选择u.idUserName，u.isActiveInd，u.employeeNbr，u.name，c.name作为CompanyName，ii.name作为IndustryName来自用户u JOIN u.idCompany c JOIN c.idIndustry i JOIN FETCH i.i18nIndustries ii WHERE u.idUserName =：username]
这里由Roo生成的.aj文件：
特权方面Users_Roo_DbManaged {
...
@ManyToOne
@JoinColumn（name =IdCompany，referencedColumnName =IdCompany，nullable = false）
私人公司Users.idCompany; ...
..
特权方面Company_Roo_DbManaged {
...
@ManyToOne
@JoinColumn（name =IdCity，referencedColumnName =IdCity，nullable = false）
私人城市Company.idCity;
@ManyToOne
@JoinColumn（name =IdIndustry，referencedColumnName =IdIndustry，nullable = false）
私有行业Company.idIndustry; ..
..
特权方面Industry_Roo_DbManaged {..
@OneToMany（mappedBy =idIndustry）
private Set< I18nIndustry> Industry.i18nIndustries; ...
您能否给我一个线索，了解这里发生的事情？
Spring MVC 3.2，
Roo 1.2.4，
MSSql数据库
谢谢大家！
--JR
关于
这些是一些问题，如果Spring Roo通过反向工程为.aj文件中的Set字段添加FetchType.LAZY，或者应该手动执行它？
这不是必需的，因为这是这种关系的默认设置（请参阅 https：// stackoverflow
如果FetchType.LAZY不存在于.aj文件中，我可以通过查询SELECT st1 FROM parentTable t1 JOIN FETCH t1.childTable st1进入select，对吗？
这使得加载关系数据。我认为你对LAZY和EAGER模式的含义有误：
- EAGER：需要在实例加载到内存中时加载值（默认为基本属性和非集合关系属性）
- LAZY：实例加载时，代理存储在属性中，并且当任何事情尝试获取数据时，加载它的形式数据库（默认为集合关系属性）
另一方面，加载一个LAZY属性需要一个数据库连接当任何东西试图获取数据时都是活着的，所以，你必须在一个非静态的 @Transactional 注解的方法中执行这段代码（读取 @Transactional JavaDoc获取更多信息）。
我建议您查看JPA规范。根据我的经验，我非常有用。
These are a couple of question, should Spring Roo through reverse engineering adding FetchType.LAZY for Set fields in .aj files or should I do it manually?
If FetchType.LAZY is not present at .aj files, I could make it through the queries " SELECT st1 FROM parentTable t1 JOIN FETCH t1.childTable st1" into the select, right ?
The point here is that I can add FetchType.LAZY to the files manually (Refactor .aj file > Push In..) and then on .java file (high risk if I want Roo to keep the control on my domain classes).
About to make it through queries, I can't do this because I'm getting:
> query specified join fetching, but the owner of the fetched association was not present in the select list [FromElement{explicit,not a collection join,fetch join,fetch non-lazy properties,classAlias=ii,role=...domain.Industry.i18nIndustries,
tableName=..I18nIndustry,
tableAlias=i18nindust3_,
origin=..Industry industry2_,
columns={industry2_.IdIndustry ,className=..domain.I18nIndustry}}]
[select u.idUserName, u.isActiveInd, u.employeeNbr, u.name, c.name as CompanyName, ii.name as IndustryName from Users u JOIN u.idCompany c JOIN c.idIndustry i JOIN FETCH i.i18nIndustries ii WHERE u.idUserName = :username ]
Here the .aj files generated by Roo:
privileged aspect Users_Roo_DbManaged {
...
@ManyToOne
@JoinColumn(name = "IdCompany", referencedColumnName = "IdCompany", nullable = false)
private Company Users.idCompany; ...
..
privileged aspect Company_Roo_DbManaged {
...
@ManyToOne
@JoinColumn(name = "IdCity", referencedColumnName = "IdCity", nullable = false)
private City Company.idCity;
@ManyToOne
@JoinColumn(name = "IdIndustry", referencedColumnName = "IdIndustry", nullable = false)
private Industry Company.idIndustry; ..
..
privileged aspect Industry_Roo_DbManaged { ..
@OneToMany(mappedBy = "idIndustry")
private Set<I18nIndustry> Industry.i18nIndustries; ...
Can you please give me a clue, about what is happening here ?
Spring MVC 3.2, Roo 1.2.4, MSSql database
Thanks folks! --JR
About
These are a couple of question, should Spring Roo through reverse engineering adding FetchType.LAZY for Set fields in .aj files or should I do it manually?
This is not needed because this is the default for this kind of relationship (see https://stackoverflow.com/a/13765381/2295657).
If FetchType.LAZY is not present at .aj files, I could make it through the queries " SELECT st1 FROM parentTable t1 JOIN FETCH t1.childTable st1" into the select, right ?
This makes a eager loading of the relationship data. I think you are in a mistake about the meaning of LAZY and EAGER modes:
- EAGER: Requires to load value when instance is loaded into memory (default for basic and no-collections-relationship properties)
- LAZY: when instance is loaded a proxy is stored in property and, when anything tries to get data, loads it form DB (default for collections-relationship properties)
On the other hand, to load a LAZY property requires a DB Connection alive when anything tries to get the data, so, you must execute this code inside a no-static, @Transactional annotated, method (read @Transactional JavaDoc for more info).
I advice you to make a look in the JPA specification. In my experience, I so useful.
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