Spring MVCでforwardするとModelが初期化されちゃうパターン

FirstController.java

package com.example;

import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

/**
 * http://localhost:8080/forward/first でアクセス
 */
@Controller
public class FirstController {

	@RequestMapping("/forward/first")
	public String hoge(HttpServletRequest req) {
		MessageForm form1 = new MessageForm();
		form1.setName("Ayaka");
		// ModelAttributeのキーと同じでセット
		req.setAttribute("messageForm", form1);
		return "forward:/forward/second";
	}
}

SecondController.java

package com.example;

import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class SecondController {

	@RequestMapping("/forward/second")
	public String foo(MessageForm form, HttpServletRequest req) {
		MessageForm form1 = (MessageForm) req.getAttribute("messageForm");
		System.out.println("second req:" + form1.getName()); // second req:Ayaka
		System.out.println("second form:" + form.getName()); // second form:null
		return "forward:/forward/third";
	}
}

ThirdController.java

package com.example;

import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class ThirdController {

	/**
	 * SecondController処理後にModelAttributeがリクエスト情報を元に初期化しちゃってる
	 */
	@RequestMapping("/forward/third")
	public void bar(MessageForm form, HttpServletRequest req) {
		MessageForm form1 = (MessageForm) req.getAttribute("messageForm");
		System.out.println("third req:" + form1.getName()); // third req:null
		System.out.println("third form:" + form1.getName()); // third form:null
	}
}