Sorting Results

Now that you've experimented with searching through data sets, let's try sorting those results.

Create Configuration File

Create a new configuration file called "ehcache-sort.xml" in your classpath and add a new cache called "sort."

<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:noNamespaceSchemaLocation="http://www.ehcache.org/ehcache.xsd"
     name="SortConfig" maxBytesLocalHeap="64M">
  <cache name="hello-world"/>
  <cache name="crud"/>
  <cache name="search">
    <searchable>
        <searchAttribute name="height"/>
        <searchAttribute name="weight"/>
        <searchAttribute name="bodyMassIndex" />
    </searchable>
  </cache>
  <cache name="sort">
    <searchable>
        <searchAttribute name="height"/>
        <searchAttribute name="weight"/>
    </searchable>
  </cache>
</ehcache>

Create Sort.java

Create and compile a Java class called Sort:

import net.sf.ehcache.Cache;
import net.sf.ehcache.CacheManager;
import net.sf.ehcache.Element;
import net.sf.ehcache.search.Attribute;
import net.sf.ehcache.search.Direction;
import net.sf.ehcache.search.Query;
import net.sf.ehcache.search.Result;
import net.sf.ehcache.search.Results;

public class Sort {

  public static void main(final String[] args) {

    // Create a cache manager using the factory method...
    final CacheManager cacheManager = CacheManager.newInstance(Sort.class
        .getResource("/ehcache-sort.xml"));

    // Retrieve the "sort" data set...
    final Cache dataSet = cacheManager.getCache("sort");

    // Create some objects...
    final Person janeAusten = new Person(1, "Jane", "Austen", 5 * 12 + 7, 130);
    final Person charlesDickens = new Person(2, "Charles", "Dickens",
        5 * 12 + 9, 160);
    final Person janeDoe = new Person(3, "Jane", "Doe", 5 * 12 + 5, 145);
    final Person alexSmith = new Person(4, "Alex", "Smith", 5 * 12 + 5, 160);

    // Put the objects into the data set...
    dataSet.put(new Element(janeAusten.getId(), janeAusten));
    dataSet.put(new Element(charlesDickens.getId(), charlesDickens));
    dataSet.put(new Element(janeDoe.getId(), janeDoe));
    dataSet.put(new Element(alexSmith.getId(), alexSmith));

    // Fetch the height and weight attributes that we'll use in the query...
    Attribute<Integer> height = dataSet.getSearchAttribute("height");
    Attribute<Integer> weight = dataSet.getSearchAttribute("weight");

    // Create a query for all people with a height greater than 5' 0", ordered
    // first by height, then by weight... this will retrieve the entire data
    // set, but we'll get to see how the results are sorted.
    final Query query = dataSet.createQuery().addCriteria(height.gt(5 * 12))
        .addOrderBy(height, Direction.DESCENDING)
        .addOrderBy(weight, Direction.DESCENDING).includeValues();

    // Execute the query...
    final Results results = query.execute();

    // Print the results...
    for (Result result : results.all()) {
      System.out.println(result.getValue());
    }
  }

  public static class Person {
    private final String firstName;
    private final String lastName;
    private final long id;
    private final int height;
    private final int weight;

    public Person(final long id, final String firstName, final String lastName,
        final int height, final int weight) {
      this.id = id;
      this.firstName = firstName;
      this.lastName = lastName;
      this.height = height;
      this.weight = weight;
    }

    public String getFirstName() {
      return firstName;
    }

    public String getLastName() {
      return lastName;
    }

    public int getHeight() {
      return height;
    }

    public int getWeight() {
      return weight;
    }

    public float getBodyMassIndex() {
      return ((float) weight / ((float) height * (float) height)) * 703;
    }

    public long getId() {
      return id;
    }

    public String toString() {
      return "[id=" + id + ", firstName=" + firstName + ", lastName="
          + lastName + ", height=" + height + " in" + ", weight=" + weight
          + " lbs" + ", bmi=" + getBodyMassIndex() + "]";
    }
  }
}

Execute

When you run the Sort program in a terminal, you should see output like this:

[id=2, firstName=Charles, lastName=Dickens, height=69 in, weight=160 lbs, bmi=23.625288]

[id=1, firstName=Jane, lastName=Austen, height=67 in, weight=130 lbs, bmi=20.358654]

[id=4, firstName=Alex, lastName=Smith, height=65 in, weight=160 lbs, bmi=26.622484]

[id=3, firstName=Jane, lastName=Doe, height=65 in, weight=145 lbs, bmi=24.126627]

The results are in descending order by height. The last two results both have the same height, so they are further ordered by weight.

Next Step

Next Step: Grouping Results ›