d10047-utility-x-json-processinng.md

Utility X, JsonObject Processing

The first batch methods in Utility X is for Json Processing, these methods start with to .

• static <T> JsonObject toJson(T entity)
• static <T> JsonObject toJson(T entity, String pojo)
• static <T> JsonObject toJsonFun(T entity, Function<JsonObject,JsonObject> convert)
• static <T> T fromJson(JsonObject data, Class<T> clazz)
• static <T> T fromJson(JsonObject data, Class<T> clazz, String pojo)
• static JsonObject fromJson(JsonObjec data, String pojo)

Above three methods could process the data type conversion of io.vertx.core.json.JsonObject. this chapter focus on these three methods usage. Before you do this testing, we'll create new Data Object for the type T.

package io.vertx.up.unity;

import java.io.Serializable;

public class D10047Obj implements Serializable {

    private String name;
    private String email;
    private Integer age;
    private boolean male;

    public String getName() {
        return this.name;
    }

    public void setName(final String name) {
        this.name = name;
    }

    public String getEmail() {
        return this.email;
    }

    public void setEmail(final String email) {
        this.email = email;
    }

    public Integer getAge() {
        return this.age;
    }

    public void setAge(final Integer age) {
        this.age = age;
    }

    public boolean isMale() {
        return this.male;
    }

    public void setMale(final boolean male) {
        this.male = male;
    }
}

Then create the resource up.god.file d10047.json, the up.god.file content should be as following:

{
    "name": "Lang",
    "email": "lang.yu@hpe.com",
    "age": 32,
    "male": true
}

1. Direct To

This chapter focus on toJson(T) method for conversion between Data Object and Json Object. The testing code should be as following:

package io.vertx.up.unity;

import io.vertx.core.json.JsonObject;
import io.vertx.quiz.TestBase;
import io.vertx.up.util.Jackson;
import org.junit.Assert;
import org.junit.Test;

public class D10047Tc extends TestBase {

    @Test
    public void testToJson() {
        final JsonObject data = this.getJson("d10047.json");
        final D10047Obj obj = Jackson.deserialize(data, D10047Obj.class);
        // Convert
        final JsonObject result = Ux.toJson(obj);
        System.out.println(result.encodePrettily());
        Assert.assertEquals(4, result.fieldNames().size());
    }
}

Here we could see that Ux.toJson method could convert a data object to JsonObject, it's useful when you want to do this conversion, because JsonObject is native data type that vert.x provided, zero system provide a way to do this conversion when you want to use your own data object. But we still recommend you use JsonObject instead of Data Object.

2. Mapping To

This chapter focus on toJson(T,String) method for conversion between Data Object and Json Object based on configuration files. Firstly you should create new configuration up.god.file:

type: "io.vertx.up.unity.D10047Obj"
mapping:
  name: username

Above up.god.file should be src/test/resources/pojo/d10047.yml, the filename is freedom. The configuration up.god.file contains two important attributes:

• type: This attribute should be full java class name, zero system will verify whether this class could be loaded.
• mapping: This attribute should be key = value for each line, it describes from -> to conversion.

Once you have finished the configuration, you could write following code:

    @Test
    public void testToJsonMapping() {

        final JsonObject data = this.getJson("d10047.json");
        final D10047Obj obj = Jackson.deserialize(data, D10047Obj.class);
        // Convert
        final JsonObject result = Ux.toJson(obj, "d10047");
        System.out.println(result.encodePrettily());
        Assert.assertEquals(4, result.fieldNames().size());
        Assert.assertEquals("Lang", result.getString("username"));
    }

Here you could see the console output:

{
  "username" : "Lang",
  "email" : "lang.yu@hpe.com",
  "age" : 32,
  "male" : true
}

The field name has been converted to username instead of original and name field has been removed from generated JsonObject. Please be careful about this operation, it's single direction that you couldn't convert back to Data Object because some fields have been updated.

3. Mapping Dynamic

This chapter focus on the last method toJsonFun(T,Function), it's for conversion between Data Object and Json Object based on the function that you provided, it's for developer to provide an interface to do this conversion by user-defined.

    @Test
    public void testToJsonFun() {
        final JsonObject data = this.getJson("d10047.json");
        final D10047Obj obj = Jackson.deserialize(data, D10047Obj.class);
        final JsonObject result = Ux.toJsonFun(obj,
                (from) -> from.put("username", from.getString("email")));
        Assert.assertEquals(result.getString("username"),
                result.getString("email"));
    }

Here you could provide a function Function<JsonObject,JsonObject>, this function could help you to convert the original JsonObject to new one, you can define your own rules.

4. Direct From

This chapter focus on fromJson(JsonObject,Class<T>) method for conversion between Data Object and Json Object. The testing code should be as following:

    @Test
    public void testFromJson() {
        final JsonObject data = this.getJson("d10047.json");
        final D10047Obj obj = Ux.fromJson(data, D10047Obj.class);
        System.out.println(obj);
        Assert.assertNotNull(obj);
    }

This method is related to toJson(T), the conversion direction is different only, here you should see following output in console

D10047Obj{name='Lang', email='lang.yu@hpe.com', age=32, male=true}

5. Mapping From

This method will involve the same mapping up.god.file:

type: "io.vertx.up.unity.D10047Obj"
mapping:
  name: username

It's related to toJson(T,String), also will use pojo up.god.file to do this conversion

    @Test
    public void testFromJsonMapping() {
        final JsonObject data = this.getJson("d10047-mapping.json");
        final D10047Obj obj = Ux.fromJson(data, D10047Obj.class, "d10047");
        System.out.println(obj);
        Assert.assertNotNull(obj);
    }

The same output will be seen in console as following:

D10047Obj{name='Lang', email='lang.yu@hpe.com', age=32, male=true}

6. Summary

These three Apis are provided for following scenarios:

• If you used some ORM framework or some lightweight Mapping framework such as Hibernate, Mybatis, Jooq etc, you'll get response data object from data access layer such Dao, Jdbc, but you want to provide normalized response to your client, you can do this conversion by these three Apis.
• If you have an old system and you want to migrate to current framework, you can write some Adapter codes here to let the Data Object could work in zero system, so you can migrate from original system to Micro Architecture more smartly.
• You can write some connector codes to do data mapping by these Apis.

These three Apis came from real project of Video App that has been hosted by zero system, because we found it's widely used and just like re-using functions, then we extract these three apis from the projects and put into standard zero system.