telnet can't work when parameter has no nullary constructor and some fields is primitive

[fibbery]

Environment

• Dubbo version: 2.6.0
• Operating System version: macOS 10.14.3
• Java version: 1.8.0_201

Steps to reproduce this issue

1. create a class has no nullary constructor and some fields is primitive

public class User implements Serializable {
    private static final long serialVersionUID = -467269449632818122L;
    private int age;
    private String name;
    public User(int age, String name) {
        this.age = age;
        this.name = name;
    }
}

2. create new method in DemoService

public interface DemoService {
    String sayHello(User user);
}

3. telnet and invoke this method

invoke sayHello({"age":1,"name":"String","class":"User"})

Expected Result

can invoke successfully

Actual Result

throw exception java.lang.IllegalArgumentException

If there is an exception, please attach the exception trace:

java.lang.IllegalArgumentException
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at com.alibaba.dubbo.common.utils.PojoUtils.newInstance(PojoUtils.java:527)
        at com.alibaba.dubbo.common.utils.PojoUtils.realize0(PojoUtils.java:436)
        at com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:196)
        at com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:86)
        at com.alibaba.dubbo.rpc.protocol.dubbo.telnet.InvokeTelnetHandler.telnet(InvokeTelnetHandler.java:138)
        at com.alibaba.dubbo.remoting.telnet.support.TelnetHandlerAdapter.telnet(TelnetHandlerAdapter.java:52)
        at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:181)
        at com.alibaba.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:50)
        at com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:79)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)

[fibbery]

should init primitive before new instance
com.alibaba.dubbo.common.utils.PojoUtils#newInstance:L527
pseudo code like this

Class<?>[] parameterTypes = constructor.getParameterTypes();
Object[] parameters = new Object[parameterTypes.length];
for (int i = 0; i < parameterTypes.length; i++) {
    if (parameterTypes[i].isPrimitive()) {
        // init primitive type 
        parameters[i] = getPrimitiveDefaultValue(parameterTypes[i]);
    }
}
return constructor.newInstance(parameters);