@OneToMany三种设置方式详解

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package footmark.springdata.jpa.domain; import java.util.ArrayList; import java.util.Collection; import javax.persistence.CascadeType; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.OneToMany; import org.apache.log4j.Logger; @Entity public class Custom { /** * Logger for this class */ private static final Logger logger = Logger.getLogger(Custom.class); private Long custId; private String detail; private Collection<Address> addresses = new ArrayList<Address>(); @Id @GeneratedValue(strategy = GenerationType.AUTO) public Long getCustId() { return custId; } public String getDetail() { return detail; } /* * 三种配置方式： * 1. @OneToMany(cascade= {CascadeType.ALL},fetch=FetchType.LAZY ,mappedBy="customId") * mappedBy属性用于双向关联实体时使用， * mappedBy属性：用在双向关联中，把关系的维护权反转 ； 跟hibernate XML映射中的property-ref一样。 * * JPA执行步骤：一、插入数据到CUSTOM表， * 二、执行getAddresses()获取需要持久化的ADDRESS（ADDRESS必须代码设置外键CUSTID）， * 三、插入数据到ADDRESS表 * * 2.@OneToMany(cascade= {CascadeType.ALL},fetch=FetchType.LAZY ) * JPA执行步骤: 一、插入数据到CUSTOM表， * 二、执行getAddresses()获取需要持久化的ADDRESS（ADDRESS代码不需要设置外键CUSTID），ADDRESS和CUSTOM关系保存在关联表中； * 三、插入数据到ADDRESS表 * 四、插入关联信息到CUSTOM_ADDRESS 表中 * 另外关联表的字段对应关系也可以手工设置， * @JoinTable(name="ref_customer_address", * joinColumns={@JoinColumn(name="customer_id",referencedColumnName="custId")}, * inverseJoinColumns={@JoinColumn(name="address_id",referencedColumnName="addrId")} * * 3.@OneToMany(cascade= {CascadeType.ALL},fetch=FetchType.LAZY ) * @JoinColumn(name="customer_id") 对应的是表中的字段，会在最后一步进行该字段的更新 * 该设置属於单向关联， 该设置需要执行三条SQL操作，不推荐；JPA推荐第一种和第二种做法； * JPA执行步骤如下：一、插入数据到CUSTOM表， * 二、执行getAddresses()获取需要持久化的ADDRESS（ADDRESS必须代码设置外键CUSTID或者将外键属性设置为可以为空）， * 三、插入数据到ADDRESS表 * 四、 然后再UPDATE ADDRESS 设置外键关系customer_id * * 4.另外多端需要初始化一个空数组 * private Collection<Address> addresses = new ArrayList<Address>(); * * */ //级联操作 @OneToMany(cascade= {CascadeType.ALL},fetch=FetchType.LAZY ,mappedBy="customId" ) // 双向关联,mappedBy="customId" 不可共存 @JoinColumn(name="customer_id") // 2 @JoinTable(name="ref_customer_address", // joinColumns={@JoinColumn(name="customer_id",referencedColumnName="custId")}, // inverseJoinColumns={@JoinColumn(name="address_id",referencedColumnName="addrId")} // ) public Collection<Address> getAddresses() { if (logger.isDebugEnabled()) { logger.debug("getAddresses() - start"); //$NON-NLS-1$ } // cascade属性和mappedBy用在一起时，一定要通过调用双方的set方法来建立关系 for (Address add :addresses) add.setCustomId(custId);//设置ADDRESS的CUSTOM外键 if (logger.isDebugEnabled()) { logger.debug("getAddresses() - end"); //$NON-NLS-1$ } return addresses; } public void pushAddress(Address add){ addresses.add(add); } public void setAddresses(Collection<Address> addresses) { this.addresses = addresses; } public void setCustId(Long custId) { this.custId = custId; } public void setDetail(String detail) { this.detail = detail; } } ------------ package footmark.springdata.jpa.domain; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; @Entity public class Address { private Long addrId; private Long customId; @Column(nullable=false) public Long getCustomId() { return customId; } public void setCustomId(Long customId) { this.customId = customId; } private String detail; @Id @GeneratedValue(strategy= GenerationType.AUTO) public Long getAddrId() { return addrId; } public String getDetail() { return detail; } public void setAddrId(Long addrId) { this.addrId = addrId; } public void setDetail(String detail) { this.detail = detail; } }