Let the DataBinder construct nested objects #20806
Comments
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Hans Desmet commented The Java ecosystem is evolving towards immutability. |
spring-projects-issues
added
type: enhancement
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I've also come across this and am interested in the enhancement. I've put together a sample that demonstrates some additional use-cases that I've highlighted below. The sample has multiple packages each demonstrating a slightly different usecase around support for immutable With GettersThis is when the immutable type has getter methods and is the same as the original issue. The resulting exception is: No GettersSometimes immutable objects inject a different value into the constructor than what is exposed via the getter methods. Currently if the custom type does not expose a getter method, the application does not throw an class Line {
private final String description;
private final Point point1;
private final Point point2;
public Line(String description, Point point1, Point point2) {
this.description = description;
this.point1 = point1;
this.point2 = point2;
}
// no getters means Spring MVC binds null values to point1 and point2
}Multiple ConstructorsAt times there are more than one constructor. Currently, Spring MVC will produce an error class Point {
private final String description;
private final int x;
private final int y;
public Point(int x, int y) {
this("default description", x, y);
}
public Point(String description, int x, int y) {
this.description = description;
this.x = x;
this.y = y;
}
public String getDescription() {
return description;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
}BuildersWhen using immutable objects, users often want to leverage Builder objects. It would be nice to be able to support the builders as shown below: class Point {
private final int x;
private final int y;
private Point(int x, int y) {
this.x = x;
this.y = y;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
public static Builder builder() {
return new Builder();
}
public static final class Builder {
private int x;
private int y;
private Builder() {
}
public Builder x(int x) {
this.x = x;
return this;
}
public Builder y(int y) {
this.y = y;
return this;
}
public Point build() {
return new Point(x, y);
}
}
}It's worth mentioning that there are a number of different styles of builders that are used, so we should probably explore supporting them as well. |
rstoyanchev
changed the title
rstoyanchev
changed the title
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In addition to changes for #26721 to have constructor initialization built into This does not cover multiple constructors and builders that @rwinch mentioned. That is related but should be considered separately I think. |
Hans Desmet opened SPR-16259 and commented
Since Spring 5, the
DataBindercan use the parametrized constructor to populate the command object upon form submission, which is a great improvement.It would be nice and handy if the
DataBindercould also use the parametrized constructor on nested objects of the command object.When using following class for the command object:
which has following class for the nested object:
upon form submission an Exception occurs:
Affects: 5.0.2
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