Spring实现简单查询操作

文章目錄

1. 1. CrudRepository
2. 2. Query creation
   1. 2.1. create Entity and declare interface Repository
   2. 2.2. Query creation
3. 3. test the Query
   1. 3.1. 保存实体
   2. 3.2. 修改PersonRepository
   3. 3.3. test continue
4. 4. Code download
   1. 4.1. Download ZIP
5. 5. 参考文章

我们知道Spring中为我们对域模型的操作提供了和多的接口。例如 CrudRepository 接口提供了复杂的CRUD功能来管理实体类。

CrudRepository

让我们来看一下CrudRepository 接口都为我们提供了什么常用的功能吧！

<S extends T> S save(S var1);

    <S extends T> Iterable<S> save(Iterable<S> var1);	//保存实体

    T findOne(ID var1);		//返回id为var1的实体

    boolean exists(ID var1);		//判断id为var1的实体是否存在

    Iterable<T> findAll();		//取出所有实体

    void delete(ID var1);		//删除id为var1的实体
    
    // … more functionality omitted.

Query creation

create Entity and declare interface Repository

scr/main/java/com.mengyunzhi/Repository

Entity

@Entity
class Person {
    @Id @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String emailAddress;
    private String lastName;
    private String firstName;

    public Person(String emailAddress, String lastName, String firstName) {
        this.emailAddress = emailAddress;
        this.lastName = lastName;
        this.firstName = firstName;
    }

    public Person(String lastName, String firstName) {
        this.lastName = lastName;
        this.firstName = firstName;
    }

    public Person() {
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getEmailAddress() {
        return emailAddress;
    }

    public void setEmailAddress(String emailAddress) {
        this.emailAddress = emailAddress;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
}

Query creation

Spring Data repository infrastructure 内置的查询生成机制对于建立实体的约束查询是很有用的。此机制的方法带有 find...By, read...By, query...By, count...By, get...By的前缀并且Spring将会自动解析其余的部分,也就是解析…部分。 你可以对实体的多个属性进行同时查询并用 And和 Or连接起来。

Example

当我们写方法的时候，会惊喜的发现Spring竟然能够自动补全我们还没有写的方法。这是不是很神奇呢！

@RepositoryRestResource(collectionResourceRel = "people", path = "people")
interface PersonRepository extends CrudRepository<Person, Long> {

    //按lastname查询
    List<Person> findByLastName(String lastname);

    //按lastname或者firstname查询
    List<Person> findByLastNameOrderByFirstName( String lastname, String firstname);

    //为查询启用静态排序
    List<Person> findByLastNameOrderByFirstNameAsc(String lastname);
}

test the Query

如果你对Spring实现 REST不熟悉的话，那请读一下上一篇文章吧！

保存实体

终端输入命令:
$ curl -i -X POST -H "Content-Type:application/json" -d '{"firstName":"Frodo","lastName":"Baggins","emailAddress":"mengynzhi@yunzhiclub"}' http://localhost:8080/people

$ curl -i -X POST -H "Content-Type:application/json" -d '{  "firstName" : "Frodo",  "lastName" : "Baggins" , "emailAddress": "mengynzhi@yunzhiclub" }' http://localhost:8080/people
HTTP/1.1 201 
Location: http://localhost:8080/people/1
Content-Type: application/hal+json;charset=UTF-8
Transfer-Encoding: chunked
Date: Sun, 28 May 2017 08:22:18 GMT

{
  "emailAddress" : "mengynzhi@yunzhiclub",
  "lastName" : "Baggins",
  "firstName" : "Frodo",
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/people/1"
    },
    "person" : {
      "href" : "http://localhost:8080/people/1"
    }
  }

发现保存成功了。

我们在终端输入 $ curl http://localhost:8080

$ curl http://localhost:8080
{
  "_links" : {
    "people" : {
      "href" : "http://localhost:8080/people"
    },
    "profile" : {
      "href" : "http://localhost:8080/profile"
    }
  }
}

同上，继续输入命令 $ curl http://localhost:8080/people/search

$ curl http://localhost:8080/people/search
{
  "_links" : {
    "findByLastName" : {
      "href" : "http://localhost:8080/people/search/findByLastName",
      "templated" : true
    },
    "findByLastNameOrderByFirstNameAsc" : {
      "href" : "http://localhost:8080/people/search/findByLastNameOrderByFirstNameAsc",
      "templated" : true
    },
    "findByLastNameOrderByFirstName" : {
      "href" : "http://localhost:8080/people/search/findByLastNameOrderByFirstName",
      "templated" : true
    },
    "self" : {
      "href" : "http://localhost:8080/people/search"
    }
  }
}

然后让我们测试第一个方法吧！$ curl http://localhost:8080/people/search/findByLastNameAndFirstName

$ curl http://localhost:8080/people/search/findByLastNameAndFirstName
{"cause":null,"message":"Unable to detect parameter names for query method com.mengyunzhi.Repository.PersonRepository.findByLastNameAndFirstNameAllIgnoreCase! Use @Param or compile with -parameters on JDK 8."}

然后我们会发现报错了，查看错误信息。因为我们需要用ajax来请求这些方法，错误信息告诉我们需要给我们函数加 @Param这个注解，我们对代码进行修改

修改PersonRepository

@RepositoryRestResource(collectionResourceRel = "people", path = "people")
interface PersonRepository extends CrudRepository<Person, Long> {

    //按lastname查询
    List<Person> findByLastName(@Param("lastname") String lastname);

    //按lastname或者firstname查询
    List<Person> findByLastNameOrderByFirstName(@Param("lastname") String lastname,
                                                         @Param("firstname") String firstname);

    //为查询启用静态排序
    List<Person> findByLastNameOrderByFirstNameAsc(@Param("lastname") String lastname);
}

test continue

终端输入命令:
http://localhost:8080/people/search/findByLastName?lastname=Baggins
就会发现Spring已经为我们查询出了结果

{
  "_embedded" : {
    "people" : [ {
      "emailAddress" : "mengynzhi@yunzhiclub",
      "lastName" : "Baggins",
      "firstName" : "Frodo",
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/people/1"
        },
        "person" : {
          "href" : "http://localhost:8080/people/1"
        }
      }
    } ]
  },
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/people/search/findByLastName?lastname=Baggins"
    }
  }
}

还剩下两个让我们自己练习一下吧！

Code download

Download ZIP

参考文章

Spring Data JPA - Reference Documentation Spring Documents