java - 编写 spring.io REST Controller 的正确方法是什么？

Question

我对 Spring 很陌生，正在尝试启动并运行一个 Web 应用程序。我可以提供静态 Material ，但很难连接到数据库。我肯定做错了一些事情，也许还有几件事是错误的。

我的代码

package com.parrit;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.util.Assert;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.parrit.models.Workspace;
import com.parrit.models.WorkspaceRepository;

@RestController
@RequestMapping("/workspace")
public class WorkspaceController {

    private final WorkspaceRepository repository;

    @Autowired
    public WorkspaceController(WorkspaceRepository repository) {
        Assert.notNull(repository, "Repository must not be null");
        this.repository = repository;
    }

    @RequestMapping(method = RequestMethod.POST)
    void save( @RequestBody String workspaceHTML) {
        Workspace ws = new Workspace();
        ws.setHTML(workspaceHTML);
        repository.save(ws);
    }
}

这个想法是让一个 Controller 在有人进入保存路径时保存一个新的存储库对象。我做错了什么/我可以去哪里了解我做错了什么。

我收到的错误消息这是一个例子:

Error creating bean with name 'workspaceController' defined in file [PROJECT_ROOT/target/classes/com/parrit/WorkspaceController.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.parrit.WorkspaceController]: No default constructor found; nested exception is java.lang.NoSuchMethodException: com.parrit.WorkspaceController.<init>()

我有那个类，并且我认为我在 bean 搜索路径中有那个类，但我真的不太确定。

这是该类，以防万一有东西

package com.parrit.models;

import org.springframework.data.jpa.repository.JpaRepository;

public interface WorkspaceRepository extends JpaRepository<Workspace, Long> {

}

Answer 1

看起来 Spring 需要一个无参构造函数......尝试将 @Autowired 注释从构造函数移动到属性并仔细检查 WorkspaceRepository 是否是 Spring bean。

@RestController
@RequestMapping("/workspace")
public class WorkspaceController {

    @Autowired
    private WorkspaceRepository repository;

    @RequestMapping(method = RequestMethod.POST)
    void save( @RequestBody String workspaceHTML) {
        Workspace ws = new Workspace();
        ws.setHTML(workspaceHTML);
        repository.save(ws);
    }
}

并检查此线程:http://forum.spring.io/forum/spring-projects/container/97753-how-to-autowire-a-bean-without-default-constructor

更新:

设置 Spring 为这些 JPA Repo 接口(interface)创建代理实例。通过 JavaConfig:

import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

@EnableJpaRepositories
class Config {}

或通过 XML 配置:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:jpa="http://www.springframework.org/schema/data/jpa"
   xsi:schemaLocation="http://www.springframework.org/schema/beans     http://www.springframework.org/schema/beans/spring-beans.xsd
      http://www.springframework.org/schema/data/jpa     http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">

   <jpa:repositories base-package="com.parrit.models"/>

</beans>

参见http://docs.spring.io/spring-data/jpa/docs/current/reference/html/#repositories.query-methods