title: spring data rest with composite primary key
body: <p>I use spring data rest for crud. But when the entity has composite primary keys, I dont know how to to get an entity by giving the primary key.</p>
  
  <p>River class:</p>
  
  <pre><code>@Entity
  public class River {
      private RiverPK id;
      private Double length;
      private Timestamp date;
      private String comment;
  
  
      @Basic
      @Column(name = "length")
      public Double getLength() {
          return length;
      }
  
      public void setLength(Double length) {
          this.length = length;
      }
  
      @Basic
      @Column(name = "date")
      public Timestamp getDate() {
          return date;
      }
  
      public void setDate(Timestamp date) {
          this.date = date;
      }
  
      @Basic
      @Column(name = "comment")
      public String getComment() {
          return comment;
      }
  
      public void setComment(String comment) {
          this.comment = comment;
      }
  
      @Id
      public RiverPK getId() {
          return id;
      }
  
      public void setId(RiverPK id) {
          this.id = id;
      }
  }
  </code></pre>
  
  <p>RiverPK class:</p>
  
  <pre><code>@Embeddable
  public class RiverPK implements Serializable {
      private String name;
      private int upcode;
      private int downcode;
  
      @Column(name = "name")
      public String getName() {
          return name;
      }
  
      public void setName(String name) {
          this.name = name;
      }
  
      @Column(name = "upcode")
      public int getUpcode() {
          return upcode;
      }
  
      public void setUpcode(int upcode) {
          this.upcode = upcode;
      }
  
      @Column(name = "downcode")
      public int getDowncode() {
          return downcode;
      }
  
      public void setDowncode(int downcode) {
          this.downcode = downcode;
      } 
  
  }
  </code></pre>
  
  <p>RiverDAO class:</p>
  
  <pre><code>@RepositoryRestResource(path = "river")
  public interface RiverDAO extends JpaRepository&lt;River, RiverPK&gt; {
  }
  </code></pre>
  
  <p>Then I can get river data by call get <a href="http://localhost:8080/river/" rel="noreferrer">http://localhost:8080/river/</a>, and also create new entity to db by call post <a href="http://localhost:8080/river/" rel="noreferrer">http://localhost:8080/river/</a> {river json}</p>
  
  <p>river json is:</p>
  
  <pre><code>id": {
  
      "name": "1",
      "upcode": 2,
      "downcode": 3
  
  },
  "length": 4.4,
  "date": 1493740800000,
  "comment": "6"
  }
  </code></pre>
  
  <p>In spring data rest doc, it should be able to call get localhost:8080/river/1 (the primary key) to get the entity which primary key is 1. This can work when the entity has only one primary key. But my entity river has composite primary keys as RiverPK. If I call get localhost:8080/river/{name='1',upcode=2,downcode=3}, it returns a error "No converter found capable of converting from type [java.lang.String] to type [com.example.db.entity.RiverPK]", I means spring use {name='1',upcode=2,downcode=3} as a String, but not RiverPK type.</p>
  
  <p>The question is how to call get\put\delete with composite primary keys as other normal entity?</p>