本文会详细展示Spring Data MongoDB是如何访问MongoDB数据库的。MongoDB是一个开源的文档型NoSQL数据库，而Spring Data MongoDB是Spring Data的模块之一，专用于访问MongoDB数据库。Spring Data MongoDB模块既提供了基于方法名的查询方式，也提供了基于注释的查询方式。
1、用Spring Data配置并管理MongoDB要安装MongoDB数据库，可以从这里下载：https://www.mongodb.org/downloads
安装过程省略。完成MongoDB的安装和运行后，可以开始应用开发了。
首先在Eclipse创建一个简单的Maven项目，并配置pom.xml管理Spring Data MongoDB项目的依赖。内容如下：
pom.xml
<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 "> <modelVersion>4.0.0</modelVersion> <groupId>SpringDataMongoDBDemo</groupId> <artifactId>SpringDataMongoDBDemo</artifactId> <version>0.0.1-SNAPSHOT</version> <dependencies> <dependency> <groupId>org.springframework.data</groupId> <artifactId>spring-data-mongodb</artifactId> <version>1.7.2.RELEASE</version> </dependency> </dependencies> </project>Eclipse会下载所需的JAR包并把依赖关系配置到项目的类路径下。现在项目的依赖关系已经完成导入，可以开始编写实际的代码了。
首先创建需要持久化到MongoDB数据库的实体类。
Person.java
package com.ch.jpa.entity; import java.util.ArrayList; import java.util.List; import org.springframework.data.annotation.Id; import org.springframework.data.annotation.PersistenceConstructor; import org.springframework.data.mongodb.core.mapping.DBRef; import org.springframework.data.mongodb.core.mapping.Document; @Document(collection = "person") public class Person { @Id private Long personId; private String name; private int age; @DBRef(db = "address") private List<Address> addresses = new ArrayList<>(); public Person() { } @PersistenceConstructor public Person(Long personId, String name, int age) { super(); this.personId = personId; this.name = name; this.age = age; } public Long getPersonId() { return personId; } public void setPersonId(Long personId) { this.personId = personId; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public List<Address> getAddresses() { return addresses; } public void setAddresses(List<Address> addresses) { this.addresses = addresses; } @Override public String toString() { return "Person [personId=" + personId + ",, age=" + age + ", addresses=" + addresses + "]"; } }注释@Document表示待持久化的数据是一个集合。如果集合没有指定名字，那么默认会使用实体类的类名作为集合名。
注释@Id表示被注解的域被映射到集合中的_id列。如果实体类中未使用此注释，那么默认名为id的域会被映射到集合中的_id列。而且此域的值由MongoDB的驱动包自动产生，它的值在在POJO中是不可用的。
注释@DBRef用于在当前的实体类中引用已有的实体类。然而，与关系数据库的情况不同，如果我们保存当前实体，它不会保存引用的相关实体。引用的相关实体的持久化是分开的。
注释@PersistenceConstructor用于标记从MongoDB数据库服务器取回数据时创建实体的构造方法。
下面是关联的Address实体类：
Address.java
package com.ch.jpa.entity; import org.springframework.data.annotation.Id; import org.springframework.data.annotation.PersistenceConstructor; import org.springframework.data.mongodb.core.mapping.Document; @Document(collection = "address") public class Address { @Id private long addressId; private String address; private String city; private String state; private long zipcode; public Address() { System.out.println("CAlling default cons"); } @PersistenceConstructor public Address(long addressId, String address, String city, String state, long zipcode) { super(); this.addressId = addressId; this.address = address; this.city = city; this.state = state; this.zipcode = zipcode; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public String getCity() { return city; } public void setCity(String city) { this.city = city; } public String getState() { return state; } public void setState(String state) { this.state = state; } public long getZipcode() { return zipcode; } public void setZipcode(long zipcode) { this.zipcode = zipcode; } @Override public String toString() { return "Address [address=" + address + ", city=" + city + ", state=" + state + ", zipcode=" + zipcode + "]"; } }