Replace commons-lang equals, hashCode, and toString with generated code

[ehrmann]

commons-lang is a relatively large library for users to include just for adding toString(), equals(), and hashCode(). This removes that dependency and uses generated code instead.

It avoids calls like Objects.hash(), Double.hashCode(), and Objects.equals() that were added in later versions of Java.

Generated code looks something like this:

public class ComplexTypesArray {
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(ComplexTypesArray.class.getName())
                .append('@')
                .append(Integer.toHexString(System.identityHashCode(this)))
                .append('[');
        sb.append("additionalProperties");
        sb.append('=');
        sb.append(((this.additionalProperties == null)?"<null>":this.additionalProperties));
        sb.append(',');
        if (sb.charAt((sb.length()- 1)) == ',') {
            sb.setCharAt((sb.length()- 1), ']');
        } else {
            sb.append(']');
        }
        return sb.toString();
    }

    @Override
    public int hashCode() {
        int result = 1;
        result = ((result* 31)+((this.additionalProperties == null)? 0 :this.additionalProperties.hashCode()));
        return result;
    }

    @Override
    public boolean equals(Object other) {
        if (other == this) {
            return true;
        }
        if ((other instanceof ComplexTypesArray) == false) {
            return false;
        }
        ComplexTypesArray rhs = ((ComplexTypesArray) other);
        return ((this.additionalProperties == rhs.additionalProperties)||((this.additionalProperties!= null)
                && this.additionalProperties.equals(rhs.additionalProperties)));
    }
}

[ehrmann]

I wasn't able to get jsonschema2pojo-gradle-plugin to pass tests. It looks like

classpath 'org.jsonschema2pojo:jsonschema2pojo-gradle-plugin:latest.integration' in jsonschema2pojo-gradle-plugin/example/java/build.gradle actually pulls in the latest repository version of jsonschema2pojo-* rather than the one from the project.

[joelittlejohn]

Great stuff. Thanks for this! Are you aware of any functional difference between the commons-lang implementations and the code you have generated?

[ehrmann]

I should look into in more (or add more tests). I tried to match the behavior of toString. Equals should generally do the right thing.

HashCode is probably different. The only time I can think of a change to hashCode making a difference is a serialized HashMap. Luckily, OpenJDK's HashMap rebuilds the map on deserialization. Since this doesn't change any fields or method signatures, these classes will have the same SerialVersionUID.

[joelittlejohn]

Great. I don't think identical behaviour is required, here (particularly, as you say, for hashCode). I only ask so that we can understand any difference that may exist, and also preempt support questions.

I'll merge this for the next release.

[ehrmann]

Cool! I might add a few tests to check the string format.

[ehrmann]

I added a test class for toString as a separate commit. It looks like the output is generally compatible. There might be an edge case, but it's really close.

[ehrmann]

@joelittlejohn Any idea when you'll make the next release?