How Can You Define Relationships in Hibernate and Spring Using Annotations?-javaTutorial-php.cn

How Can You Define Relationships in Hibernate and Spring Using Annotations?

Patricia Arquette

Release： 2024-11-03 09:10:03

Original

793 people have browsed it

How Can You Define Relationships in Hibernate and Spring Using Annotations?

Using Annotations to Define Relationships in Hibernate 4 and Spring

Uni-Directional and Bi-Directional Relationships

One-to-One Relationships

Uni-Directional:

<code class="java">class Foo {
    private Bar bar;
}

class Bar {
}</code>

Copy after login

Bi-Directional (managed by Foo class):

<code class="java">class Foo {
    @OneToOne(cascade = CascadeType.ALL)
    private Bar bar;
}

class Bar {
    @OneToOne(mappedBy = "bar")
    private Foo foo;
}</code>

Copy after login

One-to-Many Relationships

Uni-Directional using User Managed Join Table:

<code class="java">class Foo {
    @OneToMany
    @JoinTable(name = "FOO_BAR",
        joinColumns = {@JoinColumn(name = "fooId")},
        inverseJoinColumns = {@JoinColumn(name = "barId")})
    private List<Bar> bars;
}

class Bar {
    // No corresponding mapping to Foo.class
}

@Entity
@Table(name = "FOO_BAR")
class FooBar {
    private UUID fooBarId;
    private Foo foo;
    private Bar bar;
}</code>

Copy after login

Bi-Directional using Foreign Key Mapping:

<code class="java">class Foo {
    @OneToMany(mappedBy = "bar")
    private List<Bar> bars;
}

class Bar {
    @ManyToOne
    @JoinColumn(name = "fooId")
    private Foo foo;
}</code>

Copy after login

Many-to-Many Relationships

Bi-Directional using Hibernate Managed Join Table:

<code class="java">class Foo {
    @OneToMany
    @JoinTable(name = "FOO_BAR",
        joinColumns = {@JoinColumn(name = "fooId")},
        inverseJoinColumns = {@JoinColumn(name = "barId")})
    private List<Bar> bars;
}

class Bar {
    @OneToMany
    @JoinTable(name = "FOO_BAR",
        joinColumns = {@JoinColumn(name = "barId")},
        inverseJoinColumns = {@JoinColumn(name = "fooId")})
    private List<Foo> foos;
}</code>

Copy after login

Bi-Directional using User Managed Join Table:

<code class="java">class Foo {
    @OneToMany(mappedBy = "bar")
    private List<FooBar> bars;
}

class Bar {
    @OneToMany(mappedBy = "foo")
    private List<FooBar> foos;
}

@Entity
@Table(name = "FOO_BAR")
class FooBar {
    private UUID fooBarId;
    private Foo foo;
    private Bar bar;
}</code>

Copy after login

Determining Relationship Ownership

Generally, the object with the collection owns the relationship.

Choosing FetchType

Default: LAZY
Use EAGER for collections that are often used.
Consider using Hibernate.initialize() or FetchMode.SUBSELECT for lazily loaded collections needed in a specific method.

Determining Cascade Direction

Cascade operations only going in one direction unless specified.
Mark the @OneToMany annotation for cascade in the owning side of the relationship.

Orphan Removal

OrphanRemoval = true: Removes orphaned objects that are no longer referenced in any other relationship.

The above is the detailed content of How Can You Define Relationships in Hibernate and Spring Using Annotations?. For more information, please follow other related articles on the PHP Chinese website!