为什么jpa单向一对多关联thymeleaf还是会堆栈溢出?

Question

user类中有个tag类的set集合;只从user类维护关系,一对多@OneToMany@JoinTable(name="shuo_tag",inverseJoinColumns=@JoinColumn(name="tag_id"),joinColumns=@JoinColumn(name="shuo_id"))privateSettags;Tag类中没有维护关系然后我再html中[[${user}]]这样获取user就会出现以下这种错误java.lang.StackOverflowError:nullatjava.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1012)~[na:1.8.0_151]atjava.util.concurrent.ConcurrentHashMap.putIfAbsent(ConcurrentHashMap.java:1535)~[na:1.8.0_151]atjava.lang.ClassLoader.getClassLoadingLock(ClassLoader.java:463)~[na:1.8.0_151]atjava.lang.ClassLoader.loadClass(ClassLoader.java:404)~[na:1.8.0_151]atjava.lang.ClassLoader.loadClass(ClassLoader.java:411)~[na:1.8.0_151]atsun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)~[na:1.8.0_151]atjava.lang.ClassLoader.loadClass(ClassLoader.java:357)~[na:1.8.0_151]atorg.thymeleaf.util.JavaScriptUtils.printObject(JavaScriptUtils.java:365)~[thymeleaf-2.1.6.RELEASE.jar:2.1.6.RELEASE]atorg.thymeleaf.util.JavaScriptUtils.print(JavaScriptUtils.java:184)~[thymeleaf-2.1.6.RELEASE.jar:2.1.6.RELEASE]atorg.thymeleaf.util.JavaScriptUtils.printArray(JavaScriptUtils.java:227)~[thymeleaf-2.1.6.RELEASE.jar:2.1.6.RELEASE]

Answer 1

@OneToMany有一个属性叫fetch，默认是LAZY：
@Target({METHOD,FIELD})
@Retention(RUNTIME)
public@interfaceOneToMany{
/**(Optional)Whethertheassociationshouldbelazilyloadedor
*mustbeeagerlyfetched.TheEAGERstrategyisarequirementon
*thepersistenceproviderruntimethattheassociatedentities
*mustbeeagerlyfetched.TheLAZYstrategyisahinttothe
*persistenceproviderruntime.
*/
FetchTypefetch()defaultLAZY;
}
所以你要直接用，需要修改为立即加载，可以这么修改：
@OneToMany(fetch=FetchType.EAGER)
                            

Answer 2

这是thymeleaf2的bug，升级到thymeleaf3可以解决此bug；
thymeleaf2的时候是自己处理的json；thymeleaf3使用的jackson，jackson可以通过使用@JsonIgnoreProperties和@JsonIgnore注解解决两个类互相引用的问题