休眠：在sqlRestriction上使用联接表别名

如果在复杂查询中使用休眠模式，则需要使用sql。
因此，sqlRestrictions可以解决。但是，对联接表别名使用sql限制有点棘手。

将有三个表：

公司表。
员工表。
每个员工都属于一家公司，因此我们有多对一的关系。
福利表。
每个公司都有很多好处，因此我们有一对多的关系。

本示例将使用Postgresql。

CREATE DATABASE example;CREATE TABLE company (company_id SERIAL PRIMARY KEY,name TEXT NOT NULL
);CREATE TABLE employee (employee_id SERIAL PRIMARY KEY,first_name TEXT,last_name TEXT,company_id integer,CONSTRAINT fk_company FOREIGN KEY (company_id)REFERENCES company (company_id) MATCH SIMPLE
);CREATE TABLE benefit (benefit_id SERIAL PRIMARY KEY,name TEXT,company_id integer,CONSTRAINT fk_company FOREIGN KEY (company_id)REFERENCES company (company_id) MATCH SIMPLE
);INSERT INTO company (name) VALUES ('TestCompany');
INSERT INTO employee (first_name, last_name, company_id) VALUES ('Emmanouil','Gkatziouras',1);
INSERT INTO benefit (name,company_id) VALUES ('gym',1);

JPA将用于实体配置。

公司实体。

package com.gkatzioura.example.entity;import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;/*** Created by gkatziourasemmanouil on 7/12/15.*/
@Entity
@Table(name = "company")
public class Company {@Id@GeneratedValue@Column(name = "company_id")private Long Id;@ColumnString name;@OneToMany(cascade = CascadeType.ALL,fetch = FetchType.LAZY,mappedBy = "company")private Set<Benefit> benefits = new HashSet<Benefit>();public Long getId() {return Id;}public void setId(Long id) {Id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Set<Benefit> getBenefits() {return benefits;}public void setBenefits(Set<Benefit> benefits) {this.benefits = benefits;}
}

员工实体。

package com.gkatzioura.example.entity;import javax.persistence.*;/*** Created by gkatziourasemmanouil on 8/2/15.*/
@Entity
@Table(name = "employee")
public class Employee {@Id@GeneratedValue@Column(name = "employee_id")private Long id;@Column(name = "first_name")private String firstName;@Column(name = "last_name")private String lastName;@ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.LAZY)@JoinColumn(name = "company_id",referencedColumnName = "company_id")private Company company;public Long getId() {return id;}public void setId(Long id) {this.id = id;}public Company getCompany() {return company;}public void setCompany(Company company) {this.company = company;}public String getLastName() {return lastName;}public void setLastName(String lastName) {this.lastName = lastName;}public String getFirstName() {return firstName;}public void setFirstName(String firstName) {this.firstName = firstName;}
}

利益实体。

package com.gkatzioura.example.entity;import javax.persistence.*;/*** Created by gkatziourasemmanouil on 8/9/15.*/@Entity
@Table(name = "benefit")
public class Benefit {@Id@GeneratedValue@Column(name = "benefit_id")private Long id;@Column(name = "name")private String name;@ManyToOne@JoinColumn(name = "company_id")private Company company;public String getName() {return name;}public void setName(String name) {this.name = name;}public Long getId() {return id;}public void setId(Long id) {this.id = id;}public Company getCompany() {return company;}public void setCompany(Company company) {this.company = company;}
}

休眠配置

<?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><!-- Database connection settings --><property name="connection.driver_class">org.postgresql.Driver</property><property name="connection.url">jdbc:postgresql://127.0.0.1:5432/example</property><property name="connection.username">postgres</property><property name="connection.password">postgres</property><!-- JDBC connection pool (use the built-in) --><property name="connection.pool_size">1</property><!-- SQL dialect --><property name="dialect">org.hibernate.dialect.PostgreSQL9Dialect</property><!-- Enable Hibernate's automatic session context management --><property name="current_session_context_class">thread</property><!-- Disable the second-level cache  --><property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property><!-- Echo all executed SQL to stdout --><property name="show_sql">true</property><!-- Drop and re-create the database schema on startup --><property name="hbm2ddl.auto">update</property><mapping class="com.gkatzioura.example.entity.Company"/><mapping class="com.gkatzioura.example.entity.Employee"/><mapping class="com.gkatzioura.example.entity.Benefit"/></session-factory></hibernate-configuration>

创建休眠会话工厂的主类

package com.gkatzioura.example;import com.gkatzioura.example.entity.Employee;
import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Restrictions;
import org.hibernate.sql.JoinType;
import org.hibernate.type.StringType;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;/*** Created by gkatziourasemmanouil on 7/12/15.*/
public class Main {private static SessionFactory sessionFactory;private static final org.slf4j.Logger LOGGER = LoggerFactory.getLogger(SessionFactory.class);public static void main(String args[]) {sessionFactory = buildSessionFactory();getByCompanyAndBenefit("TestCompany","gym");sessionFactory.close();}public static SessionFactory buildSessionFactory() {return new Configuration().configure().buildSessionFactory();}}

假设我们要通过公司名称和特定的福利名称来提取员工，我们将添加getByCompanyAndBenefit函数。

公司名称将通过常规限制进行过滤。

但是，福利名称将由sqlRestriction过滤。

private static List<Employee> getByCompanyAndBenefit(String companyName,String benefitName) {Session session = sessionFactory.openSession();Criteria criteria = session.createCriteria(Employee.class,"employee");Criteria companyCriteria = criteria.createCriteria("company",JoinType.INNER_JOIN);companyCriteria.add(Restrictions.eq("name", companyName));Criteria benefitsAlias = companyCriteria.createCriteria("benefits",JoinType.LEFT_OUTER_JOIN);benefitsAlias.add(Restrictions.sqlRestriction("{alias}.name = ?",benefitName, StringType.INSTANCE));List<Employee> employees = criteria.list();for(Employee employee:employees) {LOGGER.error("The employee is "+employee.getFirstName());}session.close();return employees;}

对关系使用条件的createCriteria函数时，{alias}表示新条件的关联实体。

对于使用createAlias之后检索到的条件类，这是不可能的。

最后但并非最不重要的gradle文件。

group 'com.gkatzioura.example'
version '1.0-SNAPSHOT'apply plugin: 'application'
apply plugin: 'java'
apply plugin: 'idea'mainClassName = "com.gkatzioura.example.Main"sourceCompatibility = 1.8repositories {mavenLocal()mavenCentral()
}dependencies {testCompile group: 'junit', name: 'junit', version: '4.11'compile 'org.ancoron.postgresql:org.postgresql.net:9.1.901.jdbc4.1-rc9'compile 'org.slf4j:slf4j-api:1.6.6'compile 'ch.qos.logback:logback-classic:1.0.13'compile 'org.hibernate:hibernate-core:4.3.6.Final'compile 'org.hibernate:hibernate-entitymanager:4.3.6.Final'compile 'org.hibernate:hibernate-validator:5.1.1.Final'compile 'dom4j:dom4j:1.6.1'compile 'org.hibernate.javax.persistence:hibernate-jpa-2.1-api:1.0.0.Final'testCompile group: 'junit', name: 'junit', version:'3.8.1'}