Spring-MVC @ModelAttribute和@Autowired

Question

我正在尝试使用方法上的@ModelAttribute an初始化一个对象。当调用URL "/p/PPP/scope“时，会发生奇怪的事情。在调用@ModelAttribute方法时，ProjectService似乎没有被实例化，但是在调用show()方法时它就在那里。有谁知道这里面有什么不对吗？

以下是日志语句：

12:32:19 [DEBUG] ScopeController - getProject() - loading project for 'PPP'
12:32:19 [DEBUG] ScopeController - getProject() - projectService initialized? null
12:32:21 [DEBUG] ScopeController - show() - projectService initialized? ...project.ProjectService@20f2442e

来文提交人：

@Controller
@RequestMapping("/p/{abbr}/scope")
@SessionAttributes("project")
public class ScopeController {

    public static final String SHOW_PROJECT_PAGE = "/projects/scope/show";

    private static final Logger log = LoggerFactory.getLogger(ScopeController.class);

    @Autowired
    private ProjectService projectService;

    @ModelAttribute("project")
    private Project getProject(@PathVariable(value = "abbr") String abbr) {
        log.debug("getProject() - loading project for '{}'", abbr);
        log.debug("getProject() - projectService initialized? {}", projectService);
        // should call this method:
        // return projectService.find(abbr);
        return new Project();
    }

    @RequestMapping(method = RequestMethod.GET)
    @Transactional
    public String show() throws BindException {
        log.debug("show() - projectService initialized? {}", projectService);
        return SHOW_PROJECT_PAGE;
    }
}

Answer 1

所有带有ModelAttibute注释的方法都必须是公共的.

因此，当方法getProject是公共的-它将正常工作：

 @ModelAttribute("project")
 public Project getProject( ...

Answer 2

也许尝试几件事。

1. 更改：的签名
   • 私有项目getProject到
   • public @ResponseBody项目

​

1. 从控制器中删除@Transactional，并将它们移动到任何需要它们的服务方法中。(可以说是更好的设计实践-怀疑它是否导致了您所描述的问题)
2. 将@ModelAttribute(" Project ")注释移动到项目类
   • 即 @ModelAttribute(" Project ")公共项目get Project(){返回新项目()；}

​

所以它看起来就像：

@Controller
@RequestMapping("/p/{abbr}/scope")
@SessionAttributes("project")
public class ScopeController {

public static final String SHOW_PROJECT_PAGE = "/projects/scope/show";

private static final Logger log = LoggerFactory.getLogger(ScopeController.class);

@Autowired
private ProjectService projectService;

@RequestMapping(value = "/<yourUri for getProject>", method = RequestMethod.GET)
public @ResponseBody Project get(@PathVariable(value = "abbr") String abbr) {
    return getProject(abbr);
}

private Project getProject(String abbr) {
    log.debug("getProject() - loading project for '{}'", abbr);
    log.debug("getProject() - projectService initialized? {}", projectService);
    // should call this method:
    // return projectService.find(abbr);
    return new Project();
}

@RequestMapping(method = RequestMethod.GET)
@Transactional
public String show() throws BindException {
    log.debug("show() - projectService initialized? {}", projectService);
    return SHOW_PROJECT_PAGE;
}

}

//In your Project class 
@ModelAttribute("project")
public class Project {
//your class stuff
}

Answer 3

首先，我会将@Transactional注释放在存储/数据访问层，因为这是良好的分层Spring注释应用程序的规范。此外，您的@PathVariable注释用于检索控制器基本URI之后在URI中传递的值。因此，在不拦截URI模式的私有助手方法中使用该注释没有什么意义。