public class Servlet {

    public Entity createEntity(JSONObject json){
        String host = json.getString("host");
        String user = json.getString("user");
        String pwd = json.getString("pwd");
        String bd = json.getString("bd");
        Entity entity = new Entity(host, user, pwd, bd);

        return entity;
    }
}

public class Entity {

    private String host;
    private String user;
    private String pwd;
    private String bd;

    public Entity(String host, String user, String pwd, String bd){
        this.host = host;
        this.user = user;
        this.pwd = pwd;
        this.bd = bd;
    }

    public String getHost() {
        return host;
    }

    public void setHost(String host) {
        this.host = host;
    }

    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    public String getBd() {
        return bd;
    }

    public void setBd(String bd) {
        this.bd = bd;
    }
}