3.0.0-M2 Improved @ConstructorBinding Detection

[fabapp2]

What needs to be done

Implement the required migration

https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.0.0-M2-Release-Notes#improved-constructorbinding-detection

Example code (to discuss)

Ideal translation

TestCase 1

Given: the Spring Boot 2 has Configuration property file annotated with @ConstructorBinding and has only single constructor
Expected: the @ConstructorBinding annotation is removed for SpringBoot 3.0.X (it is not necessary anymore)

Acceptance criterias

Report
Given: class annotated with ...
When: recipe is applied..
Then: ....

Recipe
Given: class annotated with ...
When: recipe is applied..
Then: ....

Initial code:

@ConfigurationProperties(prefix = "mail")
@ConstructorBinding
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;

    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }


    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

Transformed code for SpringBoot 3.0.X:

@ConfigurationProperties(prefix = "mail")
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;

    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }


    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

case 2

[ashakirin]

TestCase 1:
Given: the Spring Boot 2 has Configuration property file annotated with @ConstructorBinding and has only single constructor
Expected: the @ConstructorBinding annotation is removed for SpringBoot 3.0.X (it is not necessary anymore)

Initial code:

@ConfigurationProperties(prefix = "mail")
@ConstructorBinding
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;

    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }


    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

Transformed code for SpringBoot 3.0.X:

@ConfigurationProperties(prefix = "mail")
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;

    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }


    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

[sanagaraj-pivotal]

Acceptance criteria for constructor binding

Following is an overview of different test cases for constructor binding:

Following is the list of all tests cases for Constructor Binding

@ConstructorBinding on Class level and only one constructor

Input:

package com.example.config.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.ConstructorBinding;

@ConfigurationProperties(prefix = "mail")
@ConstructorBinding
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;

    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }

    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

output

package com.example.config.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "mail")
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;

    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }

    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

@ConstructorBinding on Constructor level and only one constructor

input:

package com.example.config.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.ConstructorBinding;

@ConfigurationProperties(prefix = "mail")
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;

    @ConstructorBinding
    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }

    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

output:

package com.example.config.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "mail")
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;

    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }

    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

@ConstructorBinding on Constructor level and multiple constructors

input:

package com.example.config.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.ConstructorBinding;

@ConfigurationProperties(prefix = "mail")
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;

    @ConstructorBinding
    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }
    
    public ConfigProperties(String hello) {
    }

    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

output: Do nothing.

@ConstructorBinding on Class level and multiple constructors

input:

package com.example.config.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.ConstructorBinding;

@ConfigurationProperties(prefix = "mail")
@ConstructorBinding
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;
    
    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }
    
    public ConfigProperties(String hello) {
    }

    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

output:

package com.example.config.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.ConstructorBinding;

@ConfigurationProperties(prefix = "mail")
/*
 * TODO:
 * You need to remove ConstructorBinding on class level and move it to appropriate
 * constructor.
 * 
 * For more info visit:
 * https://bit.ly/3n5Uflt
 * */
@ConstructorBinding
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;
    
    public ConfigProperties(String hostName, int port, String from) {
        this.hostName = hostName;
        this.port = port;
        this.from = from;
    }
    
    public ConfigProperties(String hello) {
    }

    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

@ConstructorBinding on Class level but no constructors

package com.example.config.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.ConstructorBinding;

@ConfigurationProperties(prefix = "mail")
@ConstructorBinding
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;
    
    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

output:

package com.example.config.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "mail")
public class ConfigProperties {
    private String hostName;
    private int port;
    private String from;
    
    public String getHostName() {
        return hostName;
    }

    public int getPort() {
        return port;
    }

    public String getFrom() {
        return from;
    }
}

[BoykoAlex]

I looked at this recipe already and contributed to rewrite-spring openrewrite/rewrite-spring@5a37e8e

I was looking at annotations over constructors as well but at the end decided to follow exactly what release note state without doing any further work:
@ConstructorBinding is no longer needed at the type level on @ConfigurationProperties classes and should be removed. When a class or record has multiple constructors, it may still be used on a constructor to indicate which one should be used for property binding.

Just removed the type annotation from the type annotated with @ConfigurationProperties. If @ConstructorBinding is present over type with multiple constructors - remove the annotation, likely the code wasn't working properly anyway. Also, single constructor annotated i was removing it at first but the release notes don't state that we should remove anything from constructors hence i left it in. However, if you feel we should make it better for the constructors as well - I don't mind

Since I've contributed it to rewrite-spring already perhaps further corrections (if needed) we can make in rewrite-spring directly?

(As a side note - I can reanimate the code i had to handle constructors so feel free to assign to me if you like)

[ashakirin]

@ConstructorBinding on Class level but no constructors

@sanagaraj-pivotal: In this case we have to remove annotation as well

[ashakirin]

I looked at this recipe already and contributed to rewrite-spring openrewrite/rewrite-spring@5a37e8e

I was looking at annotations over constructors as well but at the end decided to follow exactly what release note state without doing any further work: @ConstructorBinding is no longer needed at the type level on @ConfigurationProperties classes and should be removed. When a class or record has multiple constructors, it may still be used on a constructor to indicate which one should be used for property binding.

Just removed the type annotation from the type annotated with @ConfigurationProperties. If @ConstructorBinding is present over type with multiple constructors - remove the annotation, likely the code wasn't working properly anyway. Also, single constructor annotated i was removing it at first but the release notes don't state that we should remove anything from constructors hence i left it in. However, if you feel we should make it better for the constructors as well - I don't mind

Since I've contributed it to rewrite-spring already perhaps further corrections (if needed) we can make in rewrite-spring directly?

(As a side note - I can reanimate the code i had to handle constructors so feel free to assign to me if you like)

@BoykoAlex:

• for the case @ConstructorBinding on class level and multiple constructors we decided to leave annotation and generate TODO for the user. Compilation error will be easy to find as runtime one
• in case of single annotated constructor release notes explicitly says that it is not really necessary:

Improved @ConstructorBinding Detection
When using constructor bound @ConfigurationProperties the @ConstructorBinding annotation is no longer required if the class has a single parameterized constructor. If you have more than one constructor, you’ll still need to use @ConstructorBinding to tell Spring Boot which one to use.

For most users, this updated logic will allow for simpler @ConfigurationProperties classes. If, however, you have a @ConfigurationProperties and you want to inject beans into the constructor rather than binding it, you’ll now need to add an @Autowired annotation.

yes, we can update rewrite-spring recipe directly or add this functionality into our spring-boot-update-30 module and synchronise all changes at the end, as we agreed

[fabapp2]

Provided to OpenRewrite: openrewrite/rewrite-spring#204