初入spring boot（八 ）Spring Data REST

　　1. 什么是Spring Data REST

　　Spring Data JPA是基于Spring Data 的Repository之上，可以将Repository自动输出为REST资源。目前Spring Data REST支持将Spring Data JPA、Spring Data MongoDB、Spring Data Neo4j、Spring Data Gemfire以及Spring Data Cassandra的Repository自动转换成REST服务。

　　2. Spring mvc中配置使用Spring Data REST

　　Spring Data REST的配置是定义在RepositoryRestMvcConfiguration配置类中已经配置好了，我们可以通过继承此类或者直接在自己的配置类上@Import此配置类

　　3. Spring boot的支持　　

　　Spring Boot对Spring Data REST的自动配置放置在rest包中

通过SpringBootRestConfiguration类的源码我们可以得出，Spring Boot已经为我们自动配置了RepositoryRestConfiguration，所以在Spring boot中使用Spring Data REST只需引入spring-boot-starter-data-rest的依赖，无须任何配置即可使用。

Spring boot通过在application.properties中配置以“spring.data.rest”为前缀的属性来配置RepositoryRestConfiguration

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.annotation.Order;
import org.springframework.data.rest.core.config.RepositoryRestConfiguration;
import org.springframework.data.rest.webmvc.config.RepositoryRestConfigurerAdapter;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

@Order(0)
class SpringBootRepositoryRestConfigurer extends RepositoryRestConfigurerAdapter {

    @Autowired(required = false)
    private Jackson2ObjectMapperBuilder objectMapperBuilder;

    @Autowired
    private RepositoryRestProperties properties;

    @Override
    public void configureRepositoryRestConfiguration(RepositoryRestConfiguration config) {
        this.properties.applyTo(config);
    }

    @Override
    public void configureJacksonObjectMapper(ObjectMapper objectMapper) {
        if (this.objectMapperBuilder != null) {
            this.objectMapperBuilder.configure(objectMapper);
        }
    }

}

@ConfigurationProperties(prefix = "spring.data.rest")
public class RepositoryRestProperties {

    /**
     * Base path to be used by Spring Data REST to expose repository resources.
     */
    private String basePath;

    /**
     * Default size of pages.
     */
    private Integer defaultPageSize;

    /**
     * Maximum size of pages.
     */
    private Integer maxPageSize;

    /**
     * Name of the URL query string parameter that indicates what page to return.
     */
    private String pageParamName;

    /**
     * Name of the URL query string parameter that indicates how many results to return at
     * once.
     */
    private String limitParamName;

    /**
     * Name of the URL query string parameter that indicates what direction to sort
     * results.
     */
    private String sortParamName;

    /**
     * Strategy to use to determine which repositories get exposed.
     */
    private RepositoryDetectionStrategies detectionStrategy = RepositoryDetectionStrategies.DEFAULT;

    /**
     * Content type to use as a default when none is specified.
     */
    private MediaType defaultMediaType;

    /**
     * Return a response body after creating an entity.
     */
    private Boolean returnBodyOnCreate;

    /**
     * Return a response body after updating an entity.
     */
    private Boolean returnBodyOnUpdate;

    /**
     * Enable enum value translation via the Spring Data REST default resource bundle.
     * Will use the fully qualified enum name as key.
     */
    private Boolean enableEnumTranslation;

    public String getBasePath() {
        return this.basePath;
    }

    public void setBasePath(String basePath) {
        this.basePath = basePath;
    }

    public Integer getDefaultPageSize() {
        return this.defaultPageSize;
    }

    public void setDefaultPageSize(Integer defaultPageSize) {
        this.defaultPageSize = defaultPageSize;
    }

    public Integer getMaxPageSize() {
        return this.maxPageSize;
    }

    public void setMaxPageSize(Integer maxPageSize) {
        this.maxPageSize = maxPageSize;
    }

    public String getPageParamName() {
        return this.pageParamName;
    }

    public void setPageParamName(String pageParamName) {
        this.pageParamName = pageParamName;
    }

    public String getLimitParamName() {
        return this.limitParamName;
    }

    public void setLimitParamName(String limitParamName) {
        this.limitParamName = limitParamName;
    }

    public String getSortParamName() {
        return this.sortParamName;
    }

    public void setSortParamName(String sortParamName) {
        this.sortParamName = sortParamName;
    }

    public RepositoryDetectionStrategies getDetectionStrategy() {
        return this.detectionStrategy;
    }

    public void setDetectionStrategy(RepositoryDetectionStrategies detectionStrategy) {
        this.detectionStrategy = detectionStrategy;
    }

    public MediaType getDefaultMediaType() {
        return this.defaultMediaType;
    }

    public void setDefaultMediaType(MediaType defaultMediaType) {
        this.defaultMediaType = defaultMediaType;
    }

    public Boolean getReturnBodyOnCreate() {
        return this.returnBodyOnCreate;
    }

    public void setReturnBodyOnCreate(Boolean returnBodyOnCreate) {
        this.returnBodyOnCreate = returnBodyOnCreate;
    }

    public Boolean getReturnBodyOnUpdate() {
        return this.returnBodyOnUpdate;
    }

    public void setReturnBodyOnUpdate(Boolean returnBodyOnUpdate) {
        this.returnBodyOnUpdate = returnBodyOnUpdate;
    }

    public Boolean getEnableEnumTranslation() {
        return this.enableEnumTranslation;
    }

    public void setEnableEnumTranslation(Boolean enableEnumTranslation) {
        this.enableEnumTranslation = enableEnumTranslation;
    }

    public void applyTo(RepositoryRestConfiguration configuration) {
        if (this.basePath != null) {
            configuration.setBasePath(this.basePath);
        }
        if (this.defaultPageSize != null) {
            configuration.setDefaultPageSize(this.defaultPageSize);
        }
        if (this.maxPageSize != null) {
            configuration.setMaxPageSize(this.maxPageSize);
        }
        if (this.pageParamName != null) {
            configuration.setPageParamName(this.pageParamName);
        }
        if (this.limitParamName != null) {
            configuration.setLimitParamName(this.limitParamName);
        }
        if (this.sortParamName != null) {
            configuration.setSortParamName(this.sortParamName);
        }
        if (this.detectionStrategy != null) {
            configuration.setRepositoryDetectionStrategy(this.detectionStrategy);
        }
        if (this.defaultMediaType != null) {
            configuration.setDefaultMediaType(this.defaultMediaType);
        }
        if (this.returnBodyOnCreate != null) {
            configuration.setReturnBodyOnCreate(this.returnBodyOnCreate);
        }
        if (this.returnBodyOnUpdate != null) {
            configuration.setReturnBodyOnUpdate(this.returnBodyOnUpdate);
        }
        if (this.enableEnumTranslation != null) {
            configuration.setEnableEnumTranslation(this.enableEnumTranslation);
        }
    }

}

实战演练

1.定义实体类

2.定义Repository

3.测试

@Entity
public class Person {
    @Id 
    @GeneratedValue
    private Long id;
    
    private String name;
    
    private Integer age;
    
    private String address;
    
    
    
    public Person() {
        super();
    }
    public Person(Long id, String name, Integer age, String address) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.address = address;
    }
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }


}

public interface PersonRepository extends JpaRepository<Person, Long> {
    
    Person findByNameStartsWith(@Param("name")String name);
}

GET请求

　　http://localhost:8080/psersons　　　　获取列表

　　http://localhost:8080/1　　　　　　　　获取id为1的对象

　　在上面的自定义Repository中定义了findByNameStartsWith方法，若想此方法也暴露为REST资源，需做如下修改

public interface PersonRepository extends JpaRepository<Person, Long> {
    
    @RestResource(path = "nameStartsWith", rel = "nameStartsWith")
    Person findByNameStartsWith(@Param("name")String name);
}

此时使用GET访问http://localhost:8080/persons/search/nameStartsWith?name=kevin,可实现查询操作

　　http://localhost:8080/persons/?page=1&size=2　　　　分页查询，page-1即第2页，size=2即每页数量为2

　　http://localhost:8080/persons/?sort=age,desc　　　　  排序，即按照age属性倒序

POST请求

　　http://localhost:8080/persons ,并将数据放到请求体中　　　　　　保存

　　http://localhost:8080/persons/21,并将数据放到请求体中　　　　  更新

DELETE请求

　　http://localhost:8080/persons/21    　　　　　　　　　　　　　 删除

4. 定制

　　（1）定制根路径

　　在上面的实战例子中，我们访问的REST资源的路径是在根目录下的，即http://localhost:8080/persos，如果我们需要定制根路径的话，只需要在Spring Boot的application.properties中添加定义 spring.data.rest.base-path= /api 此时REST资源的路径变成了http://localhost:8080/api/persons

　　（2）定制节点路径

　　上例实战中，我们的节点路径为http://localhost:8080/persons，这是Spring Data REST的默认规则，就是在实体类之后加“s”来形成路径。如果要对映射的名称进行修改的话，需要在实体类Repository上使用@RepositoryRestResource注解的path属性进行修改

@RepositoryRestResource(path = "people")
public interface PersonRepository extends JpaRepository<Person, Long> {
    
    @RestResource(path = "nameStartsWith", rel = "nameStartsWith")
    Person findByNameStartsWith(@Param("name")String name);

}

此时访问REST服务的地址变成http://localhost:8080/api/people