Javers

Question

我有2个类:

@Data
@Builder
public class Boss {
    
    private String name;
    
    private List<Employee> subordinates;
}

@Data
@Builder
public class Employee {
    
    private String name;
    
    private Boolean hasDrivingLicense;
    
    private List<Employee> colleagues;
}

还有我自己定义的比较器（规则）：

public class StringComparator implements CustomValueComparator<String> {

    public boolean equals(String s, String t1) {
        return (s != null && s.equals("") && t1 == null) || (s == null && t1 !=  null && t1.equals(""));
    }

    public String toString(String s) {
        return s;
    }
}

public class CollectionComparator<T> implements CustomValueComparator<Collection<T>> {
    
    public boolean equals(Collection<T> ts, Collection<T> t1) {
        return (ts == null && t1 != null && t1.isEmpty()) || (ts != null && ts.isEmpty() && t1 == null);
    }

    public String toString(Collection<T> ts) {
        return ts.toString();
    }
}

public class  BooleanComparator implements CustomValueComparator<Boolean> {

    public boolean equals(Boolean aBoolean, Boolean t1) {
        return (aBoolean == null && t1 != null && t1.equals(false)) 
                || (aBoolean != null && aBoolean.equals(false) && t1 == null);
    }

    public String toString(Boolean aBoolean) {
        return aBoolean.toString();
    }
}

定义了这些比较器，以便将空字符串视为与 null 相同，将空集合视为与 null 相同，将布尔 false 视为与 null 相同。在主要方法中，我尝试比较 2 个对象，以检查定义的比较器是否有效。

public static void main(String[] args) {

        Employee employee1 = Employee.builder()
                .name("Krzysztof")
                .colleagues(new ArrayList<>())
                .hasDrivingLicense(false)
                .build();

        Employee employee2 = Employee.builder()
                .name("Krzysztof")
                .colleagues(null)
                .hasDrivingLicense(null)
                .build();

        Boss boss1 = Boss.builder()
                .name("")
                .subordinates(Arrays.asList(employee1))
                .build();

        Boss boss2 = Boss.builder()
                .name(null)
                .subordinates(Arrays.asList(employee2))
                .build();

        final Javers javers = JaversBuilder.javers()
                .registerValue(CollectionComparator.class)
                .registerValue(StringComparator.class)
                .registerValue(BooleanComparator.class)
                .build();
        final Diff diff = javers.compare(boss1, boss2);

        System.out.println(diff.getChanges().size() == 0);
        System.out.println(diff.getChanges().size());
        System.out.println(diff);
    }

不幸的是，比较没有按预期进行。在 JaversBuilder 中，我尝试添加 .registerValue(String.class, (a, b) -> StringUtils.equals(a,b)) 但它也不起作用。打印结果：

false
2
Diff:
* changes on Boss/ :
  - 'name' value changed from '' to ''
  - 'subordinates/0.hasDrivingLicense' value changed from 'false' to ''

我应该更改什么才能使其正常工作。如果比较器正常工作在此示例中，diff 不会有任何更改

Answer 1

我解决了我的问题。覆盖接口 CustomPropertyComparator 就足够了。

    public class StringComparator2 implements CustomPropertyComparator<String, SetChange> {
        @Override
        public Optional<SetChange> compare(String s, String t1, PropertyChangeMetadata propertyChangeMetadata, Property property) {
            // compare           
     }

     public boolean equals(String s, String t1) {
            // equals like above
     }

     public String toString(String s) {
            // toString like above
     }
}

在主要方法中：

        final Javers javers = JaversBuilder.javers()
                .registerCustomType(String.class, new StringComparator2())
                .registerCustomType(Boolean.class, new BooleanComparator2())
                .build();
        final Diff diff = javers.compare(boss1, boss2);

        System.out.println(diff.getChanges().size() == 0);
        System.out.println(diff.getChanges().size());
        System.out.println(diff);

而且我发现 JaVers 就是这样工作的，并将 null 视为空集合。所以不需要 CollectionComparator。

Answer 2

我认为这个问题是由于您假设 CustomValueComparators 可以为空值提供一些自定义逻辑造成的。这种假设是合理的，但却是错误的。当前，CustomValueComparators 始终获取非空值进行比较。 Javers 自己处理 nuls。

我创建了一个问题来管理这个 https://github.com/javers/javers/issues/1075

Javers - 使用定义的规则比较字符串、集合和布尔值

Javers - comparison String, Collection and Boolean with defined rules

java

string

collections

boolean