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[英]Hibernate - failed to lazily initialize a collection of role: could not initialize proxy - no Session
[英]Hibernate- failed to lazily initialize a collection of role: beans.Language.patients, could not initialize proxy - no Session
我使用休眠來創建一個休息 api。 我創建了一個方法來獲取表中的所有項目。
public List<Language> getAllLanguages(Session session) {
List<Language> languages=(List<Language>)session.createQuery("from Language").list();
return languages;
}
這是我的 Language.java
public class Language implements java.io.Serializable {
private Integer idlanguage;
private String language;
private Set<Patient> patients = new HashSet<Patient>(0);
public Language() {
}
public Language(String language) {
this.language = language;
}
public Language(String language, Set<Patient> patients) {
this.language = language;
this.patients = patients;
}
public Integer getIdlanguage() {
return this.idlanguage;
}
public void setIdlanguage(Integer idlanguage) {
this.idlanguage = idlanguage;
}
public String getLanguage() {
return this.language;
}
public void setLanguage(String language) {
this.language = language;
}
public Set<Patient> getPatients() {
return this.patients;
}
public void setPatients(Set<Patient> patients) {
this.patients = patients;
}
}
這是我的 Patient.java
// Generated Sep 14, 2016 4:33:23 PM by Hibernate Tools 4.3.1
import beans.DiabetesType;
import beans.Illness;
import beans.Language;
import beans.Reminder;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;
/**
* Patient generated by hbm2java
*/
public class Patient implements java.io.Serializable {
private Integer idpatient;
private DiabetesType diabetesType;
private Language language;
private String customId;
private String diabetesOther;
private String firstName;
private String lastName;
private String userName;
private String password;
private Date dateCreated;
private Date lastUpdated;
private Set<Illness> illnesses = new HashSet<Illness>(0);
private Set<Reminder> reminders = new HashSet<Reminder>(0);
public Patient() {
}
public Patient(Integer idpatient, String password) {
this.idpatient = idpatient;
this.password = password;
}
public Patient(DiabetesType diabetesType, Language language, String customId, String firstName, String userName, String password, Date lastUpdated) {
this.diabetesType = diabetesType;
this.language = language;
this.customId = customId;
this.firstName = firstName;
this.userName = userName;
this.password = password;
this.lastUpdated = lastUpdated;
}
public Patient(DiabetesType diabetesType, Language language, String customId, String diabetesOther, String firstName, String lastName, String userName, String password, Date dateCreated, Date lastUpdated, Set<Illness> illnesses, Set<Reminder> reminders) {
this.diabetesType = diabetesType;
this.language = language;
this.customId = customId;
this.diabetesOther = diabetesOther;
this.firstName = firstName;
this.lastName = lastName;
this.userName = userName;
this.password = password;
this.dateCreated = dateCreated;
this.lastUpdated = lastUpdated;
this.illnesses = illnesses;
this.reminders = reminders;
}
public Integer getIdpatient() {
return this.idpatient;
}
public void setIdpatient(Integer idpatient) {
this.idpatient = idpatient;
}
public DiabetesType getDiabetesType() {
return this.diabetesType;
}
public void setDiabetesType(DiabetesType diabetesType) {
this.diabetesType = diabetesType;
}
public Language getLanguage() {
return this.language;
}
public void setLanguage(Language language) {
this.language = language;
}
public String getCustomId() {
return this.customId;
}
public void setCustomId(String customId) {
this.customId = customId;
}
public String getDiabetesOther() {
return this.diabetesOther;
}
public void setDiabetesOther(String diabetesOther) {
this.diabetesOther = diabetesOther;
}
public String getFirstName() {
return this.firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return this.lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getUserName() {
return this.userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return this.password;
}
public void setPassword(String password) {
this.password = password;
}
public Date getDateCreated() {
return this.dateCreated;
}
public void setDateCreated(Date dateCreated) {
this.dateCreated = dateCreated;
}
public Date getLastUpdated() {
return this.lastUpdated;
}
public void setLastUpdated(Date lastUpdated) {
this.lastUpdated = lastUpdated;
}
public Set<Illness> getIllnesses() {
return this.illnesses;
}
public void setIllnesses(Set<Illness> illnesses) {
this.illnesses = illnesses;
}
public Set<Reminder> getReminders() {
return this.reminders;
}
public void setReminders(Set<Reminder> reminders) {
this.reminders = reminders;
}
}
重要提示:bean 和映射是通過 NetBeans 從 MySQL 數據庫逆向工程的。 調用getAllLangauges
時,我不需要獲取任何與patient
相關的數據。 我的language
表只有 2 列, idlanguage
和language
。 Patient
表有language table
鍵
在 rest api 中使用此方法之前,它完美地工作,沒有任何異常。 但是當我在 rest api 中使用它時,它在那里創建了一個復雜性。
我沒有在這里使用注釋。 我使用 hibernate 逆向工程向導來映射上面的實體。 這是我的休息 api 方法。
@Path("/language")
public class LanguageJSONService {
@GET
@Path("/getAllLanguages")
@Produces(MediaType.APPLICATION_JSON)
public List<Language> getAllLanguages(){
LanguageService languageService=new LanguageService();
List<Language> list = languageService.getAllLanguages();
return list;
}
}
這就是我調用方法的方式,
Client client = ClientBuilder.newClient();
List<Language> list = client.target("http://localhost:8080/simple_rest/rest")
.path("/language/getAllLanguages")
.request(MediaType.APPLICATION_JSON)
.get(new GenericType<List<Language>>() {
});
for (int i = 0; i < list.size(); i++) {
System.out.println("Id - " + list.get(i).getIdlanguage() + " Language - " + list.get(i).getLanguage());
}
當我調用方法時,
failed to lazily initialize a collection of role: beans.Language.patients, could not initialize proxy - no Session (through reference chain: java.util.ArrayList[0]->beans.Language["patients"])
發生。
有趣的是,如果我沒有關閉會話,那么我會得到如下輸出,這完全是別的東西,似乎它正在嘗試顯示其外鍵表和它們的外鍵表等等......
[{"idlanguage":1,"language":"English","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":{"iddiabetesType":1,"type":"Sever","patients":
[{"idpatient":1,"diabetesType":
對這個問題有什么想法嗎?
更新
我的配置文件
休眠文件.cfg.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="show_sql">true</property>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/*****</property>
<property name="hibernate.connection.username">*****</property>
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">20</property>
<property name="hibernate.c3p0.timeout">3000</property>
<property name="hibernate.c3p0.max_statements">50</property>
<property name="hibernate.c3p0.idle_test_period">300</property>
<property name="hibernate.c3p0.testConnectionOnCheckout">true</property>
<property name="hibernate.c3p0.preferredTestQuery">SELECT 1</property>
<property name="hibernate.connection.password">************</property>
<mapping resource="beans/Reminder.hbm.xml"/>
<mapping resource="beans/Food.hbm.xml"/>
<mapping resource="beans/Patient.hbm.xml"/>
<mapping resource="beans/Illness.hbm.xml"/>
<mapping resource="beans/Language.hbm.xml"/>
</session-factory>
</hibernate-configuration>
語言.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<!-- Generated Sep 14, 2016 4:33:23 PM by Hibernate Tools 4.3.1 -->
<hibernate-mapping>
<class name="beans.Language" table="language" catalog="myglukose" optimistic-lock="version">
<id name="idlanguage" type="java.lang.Integer">
<column name="idlanguage" />
<generator class="identity" />
</id>
<property name="language" type="string">
<column name="language" length="45" not-null="true" />
</property>
<set name="patients" table="patient" inverse="true" lazy="true" fetch="select">
<key>
<column name="language_idlanguage" not-null="true" />
</key>
<one-to-many class="beans.Patient" />
</set>
</class>
</hibernate-mapping>
這是我的患者映射文件,
病人.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<!-- Generated Sep 14, 2016 4:33:23 PM by Hibernate Tools 4.3.1 -->
<hibernate-mapping>
<class name="beans.Patient" table="patient" catalog="myglukose" optimistic-lock="version">
<id name="idpatient" type="java.lang.Integer">
<column name="idpatient" />
<generator class="identity" />
</id>
<many-to-one name="diabetesType" class="beans.DiabetesType" fetch="select">
<column name="diabetes_type_iddiabetes_type" not-null="true" />
</many-to-one>
<many-to-one name="language" class="beans.Language" fetch="select">
<column name="language_idlanguage" not-null="true" />
</many-to-one>
<property name="customId" type="string">
<column name="custom_id" length="45" not-null="true" />
</property>
<property name="diabetesOther" type="string">
<column name="diabetes_other" length="45" />
</property>
<property name="firstName" type="string">
<column name="first_name" length="100" not-null="true" />
</property>
<property name="lastName" type="string">
<column name="last_name" length="100" />
</property>
<property name="userName" type="string">
<column name="user_name" length="45" not-null="true" />
</property>
<property name="password" type="string">
<column name="password" length="45" not-null="true" />
</property>
<property name="dateCreated" type="timestamp">
<column name="date_created" length="19" />
</property>
<property name="lastUpdated" type="timestamp">
<column name="last_updated" length="19" not-null="true">
<comment>Stores the basic information of the patient</comment>
</column>
</property>
<set name="illnesses" table="illness" inverse="true" lazy="true" fetch="select">
<key>
<column name="patient_idpatient" not-null="true" />
</key>
<one-to-many class="beans.Illness" />
</set>
<set name="reminders" table="reminder" inverse="true" lazy="true" fetch="select">
<key>
<column name="patient_idpatient" not-null="true" />
</key>
<one-to-many class="beans.Reminder" />
</set>
</class>
</hibernate-mapping>
您的 json 轉換器嘗試序列化整個實體,其中包含使用每種語言的所有患者的列表。 據我了解,json 中的患者列表不是預期的。 所以你有三個選項(我會考慮它們的順序):
@JsonIgnore
用於 Jackson),其他需要 java 配置。要應用第一個解決方案,請通過以下方式更新這些文件:
語言.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<!-- Generated Sep 14, 2016 4:33:23 PM by Hibernate Tools 4.3.1 -->
<hibernate-mapping>
<class name="beans.Language" table="language" catalog="myglukose" optimistic-lock="version">
<id name="idlanguage" type="java.lang.Integer">
<column name="idlanguage" />
<generator class="identity" />
</id>
<property name="language" type="string">
<column name="language" length="45" not-null="true" />
</property>
</class>
</hibernate-mapping>
語言.java
public class Language implements java.io.Serializable {
private Integer idlanguage;
private String language;
protected Language() {
}
public Language(String language) {
this.language = language;
}
public Integer getIdlanguage() {
return this.idlanguage;
}
protected void setIdlanguage(Integer idlanguage) {
this.idlanguage = idlanguage;
}
public String getLanguage() {
return this.language;
}
public void setLanguage(String language) {
this.language = language;
}
}
我已將 no-arg 構造函數和setId
方法更新為protected
。 您甚至可以將它們更新為private
:只有 hibernate 應該使用它們(並且它可以使用私有字段/方法)。
當您嘗試訪問惰性字段時,您需要在關閉休眠會話之前執行此操作。
當您從會話的上下文中退出時,如果需要,休眠無法訪問數據庫,因此會拋出LazyInitializationException
。
從javadoc :
表示訪問會話上下文之外未獲取的數據。 例如,在會話關閉后訪問未初始化的代理或集合時。
從目前的解釋來看,我看不出你在做什么:language.getPatients();
但是,如果您正在編寫 HQL 查詢以訪問來自語言實體的所有患者,那么我認為您應該使用 join 。 因為我可以看到與 beans.Language.patients 中的 LazyInitializationException 相關的異常。
所以我會建議下面的代碼......檢查它是否對你有用..
public List<Language> getAllLanguages(Session session) {
List<Language> languages=(List<Language>)session.createQuery("from Language as l JOIN l.patients").list();
return languages;
}
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