java - HazelCast:SqlPredicate 问题

Question

我刚开始使用 HazelCast。我有一个键和值的映射，值是对象列表。我试图在 map 上使用 SqlPredicate 来过滤值。代码片段:

private void testHazelCast() {
    final Employee e1 = new Employee("A", 20, 30);
    final Employee e2 = new Employee("C", 25, 45);
    final Employee e3 = new Employee("B", 30, 35);
    final Employee e4 = new Employee("F", 35, 30);
    final Employee e5 = new Employee("E", 40, 40);
    final Employee e6 = new Employee(null, 40, 20);
    final Employee e7 = new Employee("F", 60, 55);

    List<Employee> employeeList_1 = new ArrayList<Employee>() {{add(e1);add(e2);}};
    List<Employee> employeeList_2 = new ArrayList<Employee>() {{add(e3);add(e4);add(e7);}};
    List<Employee> employeeList_3 = new ArrayList<Employee>() {{add(e5);}};
    List<Employee> employeeList_4 = new ArrayList<Employee>() {{add(e6);}};
    IMap<Integer, List<Employee>> map = hazelcast.getMap("employee");
    map.put(1, employeeList_1);
    map.put(2, employeeList_2);
    map.put(3, employeeList_3);
    map.put(4, employeeList_4);

    // EntryObject e = new PredicateBuilder().getEntryObject();
    // Predicate predicate_1 = e.get("name").equal("A");
    Predicate predicate = new SqlPredicate("name = A");
    Set<List<Employee>> employeeSet = (Set<List<Employee>>) map.values(predicate_1);
}

class Employee implements Serializable {
    String name;
    int age;
    int weight;

    public Employee(String name, int age, int weight) {
        this.name = name;
        this.age = age;
        this.weight = weight;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("Name: " + name + ", ");
        sb.append("Age: " + age + ", ");
        sb.append("Weight: " + weight);
        return sb.toString();
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Employee employee = (Employee) o;

        if (age != employee.age) return false;
        if (weight != employee.weight) return false;
        if (!name.equals(employee.name)) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = name.hashCode();
        result = 31 * result + age;
        result = 31 * result + weight;
        return result;
    }

    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 int getWeight() {
        return weight;
    }

    public void setWeight(int weight) {
        this.weight = weight;
    }

}    

执行上述代码时，出现异常:

Caused by: java.lang.IllegalArgumentException: There is no suitable accessor for 'name' on class 'class java.util.ArrayList'

你能告诉我我到底做错了什么吗？我知道它试图在 List 类中找到“name”元素。无论如何，我可以使用 SqlPredicate 来过滤值吗？

谢谢，拉胡尔

Answer 1

对映射的每个值执行谓词。在您的示例中，您的 map 具有 Employee 集合作为值，因此谓词将在此集合上执行。

您的谓词评估为“名称 = A 的集合”:这是无效的，因为集合没有名称。

在 Hazelcast 3.6 中，您有“自定义属性”和 ValueExtractor 的概念。您可以:

1. 创建一个类，该类拥有员工集合
2. 将此类链接到 ValueExtractor，该 ValueExtractor 收集自定义属性“name”中每个员工的姓名

参见:http://docs.hazelcast.org/docs/3.6/manual/html-single/index.html#custom-attributes

此外，拥有集合 map 并不是很有效。