1 对象导航查询介绍 对象图导航检索方式是根据已经加载的对象，导航到他的关联对象。它利用类与类之间的关系来检索对象。例如：我们通过ID查询方式查出一个客户，可以调用Customer类中的getLinkMans()方法来获取该客户的所有联系人。对象导航查询的使用要求是：两个对象之间必须存在关联关系。 查询一个对象的同时，通过此对象查询他的关联对象。 案例：客户和联系人。 1.打开IDEA工具界面如图所示，点击Create New Project。 2.选择Maven工程和JDK的版本，点击Next。如图所示： 3. 填写项目名称和保存地址，并点击Finish。如图所示: 4.导入相应的依赖jar包的代码如下：
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.txw</groupId> <artifactId>jpa-day03onetomany</artifactId> <version>1.0-SNAPSHOT</version> <!--打包的方式--> <packaging>jar</packaging> <!--锁定版本号--> <properties> <spring.version>5.0.2.RELEASE</spring.version> <hibernate.version>5.0.7.Final</hibernate.version> <slf4j.version>1.6.6</slf4j.version> <log4j.version>1.2.12</log4j.version> <c3p0.version>0.9.1.2</c3p0.version> <mysql.version>5.1.6</mysql.version> </properties> <dependencies> <!-- junit单元测试 --> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> </dependency> <!-- spring beg --> <dependency> <groupId>org.aspectj</groupId> <artifactId>aspectjweaver</artifactId> <version>1.6.8</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-aop</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context-support</artifactId> <version>${spring.version}</version> </dependency> <!-- spring对orm框架的支持包--> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-orm</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring.version}</version> </dependency> <!-- spring end --> <!-- hibernate beg --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>${hibernate.version}</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>${hibernate.version}</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-validator</artifactId> <version>5.2.1.Final</version> </dependency> <!-- hibernate end --> <!-- c3p0 beg --> <dependency> <groupId>c3p0</groupId> <artifactId>c3p0</artifactId> <version>${c3p0.version}</version> </dependency> <!-- c3p0 end --> <!-- log end --> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>${log4j.version}</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>${slf4j.version}</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>${slf4j.version}</version> </dependency> <!-- log end --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>${mysql.version}</version> </dependency> <!-- spring data jpa 的坐标--> <dependency> <groupId>org.springframework.data</groupId> <artifactId>spring-data-jpa</artifactId> <version>1.9.0.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> <version>${spring.version}</version> </dependency> <!-- el beg 使用spring data jpa 必须引入 --> <dependency> <groupId>javax.el</groupId> <artifactId>javax.el-api</artifactId> <version>2.2.4</version> </dependency> <dependency> <groupId>org.glassfish.web</groupId> <artifactId>javax.el</artifactId> <version>2.2.4</version> </dependency> <!-- el end --> </dependencies> </project>5.在resources目录下创建applicationContext.xml的代码如下：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context" xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jpa="http://www.springframework.org/schema/data/jpa" xmlns:task="http://www.springframework.org/schema/task" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd"> <!--spring 和 spring data jpa的配置--> <!-- 1.创建entityManagerFactory对象交给spring容器管理--> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="dataSource" ref="dataSource" /> <!--配置的扫描的包（实体类所在的包） --> <property name="packagesToScan" value="com.txw.domain" /> <!-- jpa的实现厂家 --> <property name="persistenceProvider"> <bean class="org.hibernate.jpa.HibernatePersistenceProvider"/> </property> <!--jpa的供应商适配器 --> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> <!--配置是否自动创建数据库表 --> <property name="generateDdl" value="false" /> <!--指定数据库类型 --> <property name="database" value="MYSQL" /> <!--数据库方言：支持的特有语法 --> <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect" /> <!--是否显示sql --> <property name="showSql" value="true" /> </bean> </property> <!--jpa的方言 ：高级的特性 --> <property name="jpaDialect" > <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" /> </property> <!--注入jpa的配置信息 加载jpa的基本配置信息和jpa实现方式（hibernate）的配置信息 hibernate.hbm2ddl.auto : 自动创建数据库表 create ： 每次都会重新创建数据库表 update：有表不会重新创建，没有表会重新创建表 --> <property name="jpaProperties" > <props> <prop key="hibernate.hbm2ddl.auto">create</prop> </props> </property> </bean> <!--2.创建数据库连接池 --> <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"> <property name="user" value="root"></property> <property name="password" value="123456"></property> <property name="jdbcUrl" value="jdbc:mysql:///jpa?characterEncoding=utf-8" ></property> <property name="driverClass" value="com.mysql.jdbc.Driver"></property> </bean> <!--3.整合spring dataJpa--> <jpa:repositories base-package="com.txw.dao" transaction-manager-ref="transactionManager" entity-manager-factory-ref="entityManagerFactory" ></jpa:repositories> <!--4.配置事务管理器 --> <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="entityManagerFactory"></property> </bean> <!-- 4.txAdvice--> <tx:advice id="txAdvice" transaction-manager="transactionManager"> <tx:attributes> <tx:method name="save*" propagation="REQUIRED"/> <tx:method name="insert*" propagation="REQUIRED"/> <tx:method name="update*" propagation="REQUIRED"/> <tx:method name="delete*" propagation="REQUIRED"/> <tx:method name="get*" read-only="true"/> <tx:method name="find*" read-only="true"/> <tx:method name="*" propagation="REQUIRED"/> </tx:attributes> </tx:advice> <!-- 5.aop--> <aop:config> <aop:pointcut id="pointcut" expression="execution(* com.txw.service.*.*(..))" /> <aop:advisor advice-ref="txAdvice" pointcut-ref="pointcut" /> </aop:config> <!--5.声明式事务 --> <!-- 6. 配置包扫描--> <context:component-scan base-package="com.txw" ></context:component-scan> </beans>6.编写客户实体类的代码如下：
package com.txw.domain; import javax.persistence.*; import java.util.HashSet; import java.util.Set; /** * 1.实体类和表的映射关系 * @Eitity * @Table * 2.类中属性和表中字段的映射关系 * @Id * @GeneratedValue * @Column * @author Adair */ @Entity @Table(name="cst_customer") @SuppressWarnings("all") //注解警告信息 public class Customer { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="cust_id") private Long custId; // 客户的主键 @Column(name="cust_address") private String custAddress; // 客户地址 @Column(name="cust_industry") private String custIndustry; // 客户所属行业 @Column(name="cust_level") private String custLevel; // 客户级别 @Column(name="cust_name") private String custName; // 客户名称 @Column(name="cust_phone") private String custPhone; // 客户的联系方式 @Column(name="cust_source") private String custSource; // 客户来源 //配置客户和联系人之间的关系（一对多关系） /** * 放弃外键维护权 * mappedBy：对方配置关系的属性名称\ * cascade : 配置级联（可以配置到设置多表的映射关系的注解上） * CascadeType.all : 所有 * MERGE ：更新 * PERSIST ：保存 * REMOVE ：删除 * fetch : 配置关联对象的加载方式 * EAGER ：立即加载 * LAZY ：延迟加载 */ @OneToMany(mappedBy = "customer",cascade = CascadeType.ALL) private Set<LinkMan> linkMans = new HashSet<>(); public Long getCustId() { return custId; } public void setCustId(Long custId) { this.custId = custId; } public String getCustAddress() { return custAddress; } public void setCustAddress(String custAddress) { this.custAddress = custAddress; } public String getCustIndustry() { return custIndustry; } public void setCustIndustry(String custIndustry) { this.custIndustry = custIndustry; } public String getCustLevel() { return custLevel; } public void setCustLevel(String custLevel) { this.custLevel = custLevel; } public String getCustName() { return custName; } public void setCustName(String custName) { this.custName = custName; } public String getCustPhone() { return custPhone; } public void setCustPhone(String custPhone) { this.custPhone = custPhone; } public String getCustSource() { return custSource; } public void setCustSource(String custSource) { this.custSource = custSource; } public Set<LinkMan> getLinkMans() { return linkMans; } public void setLinkMans(Set<LinkMan> linkMans) { this.linkMans = linkMans; } @Override public String toString() { return "Customer{" + "custId=" + custId + ", custAddress='" + custAddress + '\'' + ", custIndustry='" + custIndustry + '\'' + ", custLevel='" + custLevel + '\'' + ", custName='" + custName + '\'' + ", custPhone='" + custPhone + '\'' + ", custSource='" + custSource + '\'' + '}'; } }7.编写客户实体类的持久层代码如下：
package com.txw.dao; import com.txw.domain.Customer; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.jpa.repository.JpaSpecificationExecutor; /** * 符合SpringDataJpa的dao层接口规范 * JpaRepository<操作的实体类类型，实体类中主键属性的类型> * * 封装了基本CRUD操作 * JpaSpecificationExecutor<操作的实体类类型> * * 封装了复杂查询（分页） * @author：Adair */ @SuppressWarnings("all") // 注解警告信息 public interface CustomerDao extends JpaRepository<Customer,Long> ,JpaSpecificationExecutor<Customer> { }8.编写联系人实体类的代码如下：
package com.txw.domain; import javax.persistence.*; /** * 联系人的实体类 * @author Adair */ @Entity @Table(name = "cst_linkman") @SuppressWarnings("all") //注解警告信息 public class LinkMan { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name = "lkm_id") private Long lkmId; // 联系人编号(主键) @Column(name = "lkm_name") private String lkmName; // 联系人姓名 @Column(name = "lkm_gender") private String lkmGender; // 联系人性别 @Column(name = "lkm_phone") private String lkmPhone; // 联系人办公电话 @Column(name = "lkm_mobile") private String lkmMobile; // 联系人手机 @Column(name = "lkm_email") private String lkmEmail;// 联系人邮箱 @Column(name = "lkm_position") private String lkmPosition; // 联系人职位 @Column(name = "lkm_memo") private String lkmMemo; // 联系人备注 /** * 配置联系人到客户的多对一关系 * 使用注解的形式配置多对一关系 * 1.配置表关系 * @ManyToOne : 配置多对一关系 * targetEntity：对方的实体类字节码 * 2.配置外键（中间表） * 配置外键的过程，配置到了多的一方，就会在多的一方维护外键 */ @ManyToOne(targetEntity = Customer.class,fetch = FetchType.LAZY) @JoinColumn(name = "lkm_cust_id",referencedColumnName = "cust_id") private Customer customer; public Long getLkmId() { return lkmId; } public void setLkmId(Long lkmId) { this.lkmId = lkmId; } public String getLkmName() { return lkmName; } public void setLkmName(String lkmName) { this.lkmName = lkmName; } public String getLkmGender() { return lkmGender; } public void setLkmGender(String lkmGender) { this.lkmGender = lkmGender; } public String getLkmPhone() { return lkmPhone; } public void setLkmPhone(String lkmPhone) { this.lkmPhone = lkmPhone; } public String getLkmMobile() { return lkmMobile; } public void setLkmMobile(String lkmMobile) { this.lkmMobile = lkmMobile; } public String getLkmEmail() { return lkmEmail; } public void setLkmEmail(String lkmEmail) { this.lkmEmail = lkmEmail; } public String getLkmPosition() { return lkmPosition; } public void setLkmPosition(String lkmPosition) { this.lkmPosition = lkmPosition; } public String getLkmMemo() { return lkmMemo; } public void setLkmMemo(String lkmMemo) { this.lkmMemo = lkmMemo; } public Customer getCustomer() { return customer; } public void setCustomer(Customer customer) { this.customer = customer; } @Override public String toString() { return "LinkMan{" + "lkmId=" + lkmId + ", lkmName='" + lkmName + '\'' + ", lkmGender='" + lkmGender + '\'' + ", lkmPhone='" + lkmPhone + '\'' + ", lkmMobile='" + lkmMobile + '\'' + ", lkmEmail='" + lkmEmail + '\'' + ", lkmPosition='" + lkmPosition + '\'' + ", lkmMemo='" + lkmMemo + '\'' + '}'; } }9.编写联系人实体类持久层的代码如下：
package com.txw.dao; import com.txw.domain.LinkMan; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.jpa.repository.JpaSpecificationExecutor; /** *符合SpringDataJpa的dao层接口规范 * JpaRepository<操作的实体类类型，实体类中主键属性的类型> * * 封装了基本CRUD操作 * JpaSpecificationExecutor<操作的实体类类型> * * 封装了复杂查询（分页） * @author: Adair */ @SuppressWarnings("all") // 注解警告信息 public interface LinkManDao extends JpaRepository<LinkMan,Long >,JpaSpecificationExecutor<LinkMan> { }10.测试代码如下：
package com.txw.test; import com.txw.dao.CustomerDao; import com.txw.dao.LinkManDao; import com.txw.domain.Customer; import com.txw.domain.LinkMan; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; import org.springframework.transaction.annotation.Transactional; import java.util.Set; /** * 测试对象导航查询 */ @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = "classpath:applicationContext.xml") public class ObjectQueryTest { // 声明CustomerDao业务对象 @Autowired private CustomerDao customerDao; // 声明LinkManDao业务对象 @Autowired private LinkManDao linkManDao; //could not initialize proxy - no Session //测试对象导航查询（查询一个对象的时候，通过此对象查询所有的关联对象） @Test @Transactional // 解决在java代码中的no session问题 public void testQuery1() { //查询id为1的客户 Customer customer = customerDao.getOne(1l); //对象导航查询，此客户下的所有联系人 Set<LinkMan> linkMans = customer.getLinkMans(); for (LinkMan linkMan : linkMans) { System.out.println(linkMan); } } }运行结果如图所示： 如果没有加@Transactional会报如图所示的错误！ 修改为立即加载的代码如图所示： 编写将延迟加载改为立即加载的测试代码如下：
package com.txw.test; import com.txw.dao.CustomerDao; import com.txw.dao.LinkManDao; import com.txw.domain.Customer; import com.txw.domain.LinkMan; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; import org.springframework.transaction.annotation.Transactional; import java.util.Set; /** * 测试对象导航查询 */ @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = "classpath:applicationContext.xml") public class ObjectQueryTest { // 声明CustomerDao业务对象 @Autowired private CustomerDao customerDao; // 声明LinkManDao业务对象 @Autowired private LinkManDao linkManDao; /** * 对象导航查询： * 默认使用的是延迟加载的形式查询的 * 调用get方法并不会立即发送查询，而是在使用关联对象的时候才会差和讯 * 延迟加载！ * 修改配置，将延迟加载改为立即加载 * fetch，需要配置到多表映射关系的注解上 */ @Test @Transactional // 解决在java代码中的no session问题 public void testQuery2() { // 查询id为1的客户 Customer customer = customerDao.findOne(1l); // 对象导航查询，此客户下的所有联系人 Set<LinkMan> linkMans = customer.getLinkMans(); System.out.println(linkMans.size()); } }运行结果如图所示： 修改联系人为延迟加载的代码如图所示： 测试代码如下：
package com.txw.test; import com.txw.dao.CustomerDao; import com.txw.dao.LinkManDao; import com.txw.domain.Customer; import com.txw.domain.LinkMan; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; import org.springframework.transaction.annotation.Transactional; import java.util.Set; /** * 测试对象导航查询 */ @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = "classpath:applicationContext.xml") public class ObjectQueryTest { // 声明CustomerDao业务对象 @Autowired private CustomerDao customerDao; // 声明LinkManDao业务对象 @Autowired private LinkManDao linkManDao; /** * 从联系人对象导航查询他的所属客户 * * 默认 ： 立即加载 * 延迟加载： */ @Test @Transactional // 解决在java代码中的no session问题 public void testQuery3() { LinkMan linkMan = linkManDao.findOne(2l); // 对象导航查询所属的客户 Customer customer = linkMan.getCustomer(); System.out.println(customer); } }运行结果如图所示： 总结： 从一方查询多方。 默认：使用延迟加载。 从多方查询一方。 默认：使用立即加载。
