springboot + hibernate实现一个简单的查询功能

一,环境

idea,jdk8,oracle

二,实现效果

三,步骤

1 新建一个springboot项目

file->new->project->Spring Initializr

next->填写自己的groupid等信息->next->选择web和jpa组件

next项目就新建成功了.

2 修改为自己的maven仓库(如果想使用默认的仓库也可以不修改)

file->settings

3 修改项目为sources,便于后面新建class,package文件(这一步可以等你新建类出问题的时候才做)

file->project structure->点击下面的sources

4 在pom.xml中引入oracle依赖(正常情况是不应该写version的,由于懒得去找springboot对应的版本了,就先这样,但很容易引起冲突)

    com.oracle
    ojdbc6
    11.1.0.6.0

如果maven仓库中没有这个jar包请,去官网下载,并手动编译到本地仓库,编译命定如下

mvn install:install-file -Dfile=E:/ojdbc6.jar -DgroupId=com.oracle -DartifactId=ojdbc6 -Dversion=11.1.0.6.0 -Dpackaging=jar -DgeneratePom=true 

5 配置数据连接  application.yml文件

#配置数据库连接
spring:
  datasource:
    driver-class-name: oracle.jdbc.driver.OracleDriver
    url: jdbc:oracle:thin:@127.0.0.1:1521:orcl
    username: xiaobai
    password: 1
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
#配置端口号
server:
  port: 8080

6 编写dao,service,controller层代码

EmpDao.java

package com.yxf.springboothibernate.dao;

import com.yxf.springboothibernate.model.Emp;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;

@Repository
public interface EmpDao  extends JpaRepository {
    @Query("select t from Emp t where t.guid = :id")//无法注入empdao
    public Emp findUserById(@Param("id") String id);//参数需要用@param
}

EmpService.java与EmpServiceImpl.java

package com.yxf.springboothibernate.service;

import com.yxf.springboothibernate.model.Emp;


public interface EmpService {
    Emp findUserById(String id);
}

package com.yxf.springboothibernate.service;

import com.yxf.springboothibernate.dao.EmpDao;
import com.yxf.springboothibernate.model.Emp;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class EmpServiceImpl implements  EmpService {
    @Autowired
    private EmpDao empDao;
    @Override
    public Emp findUserById(String id) {
        return empDao.findUserById(id);
    }
}

Emp.java

package com.yxf.springboothibernate.model;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
//@Table(name="emp")
public class Emp /*implements Serializable */{
    @Id
    //@GeneratedValue
    private String guid;
    private String name;
    private double sal;
    private String deno;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getSal() {
        return sal;
    }

    public void setSal(double sal) {
        this.sal = sal;
    }

    public String getDeno() {
        return deno;
    }

    public void setDeno(String deno) {
        this.deno = deno;
    }

    public String getGuid() {
        return guid;
    }

    public void setGuid(String guid) {
        this.guid = guid;
    }

    @Override
    public String toString() {
        return "Emp{" +
                "guid='" + guid + '\'' +
                ", name='" + name + '\'' +
                ", sal=" + sal +
                ", deno='" + deno + '\'' +
                '}';
    }
}

EmpController.java

package com.yxf.springboothibernate.controller;

import com.yxf.springboothibernate.model.Emp;
import com.yxf.springboothibernate.service.EmpService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class EmpController {
    @Autowired
    private EmpService empService;
    @ResponseBody
    @RequestMapping("/query")
    public String queryEmp(){
        Emp emp = empService.findUserById("F003C33CB34349AAA0A860CC9A2D208F");
        System.out.println(emp.toString());
        return emp.toString();
    }
}

7 运行主文件

四 问题总结

在写这个demo的过程中也遇到过好几个问题,由于对hibernate的知识有些遗忘了

1 启动的时候出现如下错误

nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'empDao': 

明显是dao这个bean对象创建错误,但找了很久才发现是我的查询语句里面的表写的是emp,我数据库里面是emp,java对象是Emp

此时这里应该是使用Emp不然就会出现以上错误

2 访问的时候报以下错误

IllegalStateException: For queries with named parameters you need to use provide names for method param

需要在传的参数加上@Param

补充

数据库表字段

文件目录