What is to bind?

Question

I can’t find the meaning of Bind to explain to me what this is. I would like an example of Bind with the same java language.

Answer 1

Bind or Binding are terms used in different applications, but in general refer to how Java or any language links certain things.

Data Binding

Define how data in different formats are mapped to and from objects. There are numerous possibilities, where the most common ones are:

Binding HTTP request

It consists of mapping attributes in HTTP requests for objects or maps. How this is done depends on the framework.

JSF for example uses special tags like <h:inputText/>:

<h:inputText value="#{userController.username}" />

The above example would map the field in HTML with an attribute String username in class UserController.

Frameworks such as Spring MVC or JAX-RS compatible usually map each request parameter directly to an attribute. For example:

<input type="text" name="nome" />

It would be connected as follows:

class Usuario { 
    String nome;
    public void setNome(String nome) { ... }
}

class UsuarioController {
    @GET
    @Path("/usuario/incluir)
    public String incluir(Usuario usuario) { ... } 
}

Binding of JSON and XML

Data represented in JSON and XML can also be linked with objects using libraries such as Jackson (JSON) and JAXB (XML).

Example with Jackson:

ObjectMapper mapper = new ObjectMapper();
String json = "{'nome' : 'Maria'}";
Pessoa pessoa = mapper.readValue(json, Pessoa.class);

Binding of databases

The best known examples are JPA frameworks such as Hibernate and Eclipselink, where you can configure a class so that the data of the fields in a table is linked to the attributes of a class, it is possible to send and recover data without writing SQL clauses or recovering field by field.

Example of mapping a JPA entity:

@Entity
public class Pessoa {
    @Id
    long id;
    String nome;
    String endereco;
    ...
}

Method Binding

Another example is the method Binding or linking of methods, which means how language does to determine which is the correct method that should be called according to several factors:

• Class hierarchy, for example when a subclass overrides a method or when a class implements the interface method.
• Method overload, for example when methods of the same name receive parameters of different types one has a different number of parameters

In some cases it is possible to determine the correct method at compile time, for example if it is static or final. In the other vessels the correct method is determined at runtime, which in theory is slower since it includes further processing during the execution of the program. In fact, the JVM includes a series of optimizations that make the impact of performance virtually negligible in most cases.

Other

Other examples of Binding include:

• How MVC web frameworks decide which method to call according to the request parameters and settings.
• How Dependency Injection frameworks decide which class to inject based on criteria such as class hierarchy, annotations, and settings.

Answer 2

There is Dynamic Bind and Static Bind.

In the static bind, you have methods within your main class and call them straight into the main (the methods have to be static), e.g.:

public class Main{
    public static void varType(float var){
        System.out.println("Is an float!");
    }

    public static void varType(int var){
        System.out.println("Is an int!");
    }

    public static void varType(String var){
        System.out.println("Is an string!");
    }

    public static void main(String args[]){
        int x = 0;
        float y = 0;
        String z = "0";
        varType(x);
        varType(y);
        varType(z);
    }
}

In short, calls are made in the static method in the main methods.

The dynamic bind is created an instance of the main class to use its methods, e.g.:

public class Main{
    public void varType(float var){
        System.out.println("Is an float!");
    }

    public void varType(int var){
        System.out.println("Is an int!");
    }

    public void varType(String var){
        System.out.println("Is an string!");
    }

    public static void main(String args[]){
        int x = 0;
        float y = 0;
        String z = "0";
        Main m = new Main();
        m.varType(x);
        m.varType(y);
        m.varType(z);
    }
}

Reference: http://beginnersbook.com/2013/04/java-static-dynamic-binding/