SpringBoot项目新建遇到问题整理
Posted 青山不改，绿水长流
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1.新建了一个SpringBoot项目：只引用需要用到的spring boot相关的jar包,除此之外没有任何的配置
启动application.java报错：
APPLICATION FAILED TO START
***************************
***************************
Description:
Cannot determine embedded database driver class for database type NONE
Action:
If you want an embedded database please put a supported one on the classpath. If you have database settings to be loaded from a particular profile you may need to active it (no profiles are currently active).
--——————>原因：因为spring boot只要你在pom中引入了spring-boot-starter-data-jpa，他就会默认需要加载数据库相关的配置
你要是没有在配置文件中配置数据库相关信息，它会加载默认的配置（不存在的） 然后就报错了， 所以你要是要用数据库相关的东西 你就完善配置
不用数据库相关的东西 就不要在pom中引入相关依赖。
不用数据库相关的东西 就不要在pom中引入相关依赖。
--------------------->解决:注释掉引用的数据库相关的jar，即可正常启动
2.新建一个小项目，springboot使用1.5.16，项目启动类使用注解@SpringBootApplication，controller使用注解@Controller,浏览器输入ip地址报错：
Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Tue Jan 08 13:48:08 CST 2019
There was an unexpected error (type=Not Found, status=404).
No message available
原因： ![]()
![]()
控制器的URL路径没有找到
@controller改成@RestController页面可正常显示
3.pom.xml中配置了热启动，但是修改controller后没有重新加载，console控制台也没有加载新的内容-》热启动没有生效
查找原因：热部署依赖于项目的自动编译功能：Project->Build Automatically（自动编译）是否已经勾选，若没勾选，则需要勾选，否则热启动无用
4.SpringBoot项目启动类*Application.java：SpringBoot项目只能有一个main方法：
其中：@SpringBootApplication 等价于
@Controller
@EnableAutoConfiguration
@ComponentScan("com.yst.helloWOrld.web")
5.Junit单元测试使用MockMvc做controller接口测试
（51）直接返回字符串中含有中文---》中文乱码
JunitTest代码为：
1 package com.yst.helloWorld; 2 3 import org.junit.Before; 4 import org.junit.Test; 5 import org.springframework.boot.test.context.SpringBootTest; 6 import org.springframework.test.web.servlet.MockMvc; 7 import org.springframework.test.web.servlet.MvcResult; 8 import org.springframework.test.web.servlet.ResultHandler; 9 import org.springframework.test.web.servlet.request.MockMvcRequestBuilders; 10 import org.springframework.test.web.servlet.setup.MockMvcBuilders; 11 import com.yst.helloWorld.web.HelloWorldController; 12 13 @SpringBootTest 14 public class HelloWorldApplicationTests { 15 //使用MockMvc做controller接口测试 16 private MockMvc mockMvc; 17 18 @Before //这个方法在每个方法执行之前都会执行一遍 19 public void setUp() throws Exception { 20 mockMvc = MockMvcBuilders.standaloneSetup(new HelloWorldController()).build(); 21 } 22 @Test 23 public void getHello() throws Exception { 24 mockMvc.perform(MockMvcRequestBuilders.post("/hello")//请求的url,请求的方法是post 25 // .contentType(MediaType.APPLICATION_FORM_URLENCODED) 26 // .param("name", "value")//添加参数 27 ).andDo(new ResultHandler() { 28 @Override 29 public void handle(MvcResult result) throws Exception { 30 result.getResponse().setCharacterEncoding("UTF-8"); 31 System.out.println("结果："+result.getResponse().getContentAsString());//result.getResponse().getContentAsString()不支持中文格式 32 System.out.println("请求状态码："+result.getResponse().getStatus());//result.getResponse().getContentAsString()不支持中文格式 33 } 34 }); 35 } 36 37 // @Test 38 // public void hello() { 39 // System.out.println("hello"); 40 // } 41 // @Test 42 // public void contextLoads() { 43 // } 44 45 }
controller代码：
1 package com.yst.helloWorld.web; 2 3 import org.springframework.stereotype.Controller; 4 import org.springframework.ui.Model; 5 import org.springframework.web.bind.annotation.PathVariable; 6 import org.springframework.web.bind.annotation.RequestMapping; 7 import org.springframework.web.bind.annotation.RequestMethod; 8 import org.springframework.web.bind.annotation.RestController; 9 @RestController 10 //@Controller 11 public class HelloWorldController { 12 13 @RequestMapping(value="/hello") 14 public String hello() { 15 return "hello my world! 我的世界"; 16 } 17 18 @RequestMapping(value="/findUser/{userId}") 19 public String findUser(@PathVariable String userId, Model model) { 20 return "my User:"+userId; 21 } 22 23 @RequestMapping(value="/{textualPart:[a-z-]+}.{numericPart:[\\\\d]+}") 24 public String regularExpression( 25 @PathVariable String textualPart, 26 @PathVariable String numericPart){ 27 28 System.out.println("Textual part: " + textualPart + 29 ", numeric part: " + numericPart); 30 return "someResult"; 31 } 32 33 @RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, params="myParam=myValue") 34 public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) { 35 // implementation omitted 36 } 37 38 39 }
执行结果为：
结果：hello my world! ???? ----------》中文显示正常
请求状态码：200
---》解决方式：暂时未解决
（52）返回对象或集合：对象字段含有中文--》返回结果正常显示
controller代码：
1 package com.yst.helloWorld.web; 2 3 import org.springframework.ui.Model; 4 import org.springframework.web.bind.annotation.PathVariable; 5 import org.springframework.web.bind.annotation.RequestMapping; 6 import org.springframework.web.bind.annotation.RequestMethod; 7 import org.springframework.web.bind.annotation.RestController; 8 9 import com.yst.helloWorld.domain.User; 10 @RestController 11 public class HelloWorldController { 12 13 @RequestMapping("/getUser") 14 public User getUser() { 15 User user = new User(); 16 user.setName("王火火"); 17 user.setAge(18); 18 user.setPass("123456"); 19 return user; 20 21 }
22 }
JunitTest代码：
1 package com.yst.helloWorld; 2 3 import org.junit.Before; 4 import org.junit.Test; 5 import org.springframework.boot.test.context.SpringBootTest; 6 import org.springframework.test.web.servlet.MockMvc; 7 import org.springframework.test.web.servlet.MvcResult; 8 import org.springframework.test.web.servlet.ResultHandler; 9 import org.springframework.test.web.servlet.request.MockMvcRequestBuilders; 10 import org.springframework.test.web.servlet.setup.MockMvcBuilders; 11 import com.yst.helloWorld.web.HelloWorldController; 12 13 @SpringBootTest 14 public class HelloWorldApplicationTests { 15 //使用MockMvc做controller接口测试 16 private MockMvc mockMvc; 17 18 @Before //这个方法在每个方法执行之前都会执行一遍 19 public void setUp() throws Exception { 20 mockMvc = MockMvcBuilders.standaloneSetup(new HelloWorldController()).build(); 21 } 22 23 @Test 24 public void getUser() throws Exception { 25 mockMvc.perform(MockMvcRequestBuilders.post("/getUser"))//请求的url,请求的方法是post 26 .andDo(new ResultHandler() { 27 @Override 28 public void handle(MvcResult result) throws Exception { 29 // result.getResponse().setCharacterEncoding("UTF-8"); 30 System.out.println("结果："+result.getResponse().getContentAsString());// 31 System.out.println("请求状态码："+result.getResponse().getStatus());// 32 } 33 }); 34 } 35 36 37 38 }
结果为：
结果：{"name":"王火火","age":18,"pass":"123456"} ------》说明SpringBoot自动将对象转换为Json进行返回
请求状态码：200
若返回集合，代码如下：
1 @RequestMapping("/getUsers") 2 public List<User> getUsers() { 3 List<User> users = new ArrayList<User>(); 4 User u1 = new User(); 5 u1.setName("王火火"); 6 u1.setAge(18); 7 u1.setPass("123456"); 8 users.add(u1); 9 User u2 = new User(); 10 u2.setName("张明"); 11 u2.setAge(18); 12 u2.setPass("123"); 13 users.add(u2); 14 return users; 15 16 }
添加测试方法进行测试，返回内容为：
结果：[{"name":"王火火","age":18,"pass":"123456"},{"name":"张明","age":18,"pass":"123"}]
请求状态码：200
so，这说明不管对象/集合/嵌套对象，SpringBoot均可以将其转换为Json字符串，Spring天然对Json支持；
特别适用于给其他系统提供接口。
6.查看SpringBoot匹配的环境版本：
Spring官网：https://spring.io/--->projects--->Spring boot--->Learn--->选取一个版本，点击Reference Doc. --->往下拉：查看：
9.System Requirements 和 9.1 Servlet Containers
如图：
7.限制请求方式：@RequestMapping(method=RequestMethod.POST)
1 @RequestMapping(name = "/getUser",method=RequestMethod.POST)//为安全，只允许post请求访问 2 public User getUser() { 3 User user = new User(); 4 user.setName("王火火"); 5 user.setAge(18); 6 user.setPass("123456"); 7 return user; 8 }
若以get方式请求，会返回：org.springframework.web.HttpRequestMethodNotSupportedException: Request method \'GET\' not supported]
8.传参方式
（1）使用对象接收:适用于从页面获取值：页面中只要是属于User的属性都会被自动填充到该对象中
@RequestMapping(name = "/getUser",method=RequestMethod.POST)// public User getUser(User user) { return user; }
(2)适用url进行传参：@PathVariable（import org.springframework.web.bind.annotation.PathVariable;）
(
注意两个区别
- @PathVariable是获取url上数据的。
- @RequestParam获取请求参数的（包括post表单提交）
)
1 //注意url模板中的占位符的值必须和@PathVariable中的值相同才能完成绑定 2 @RequestMapping(name = "/getUser/{useName}",method=RequestMethod.GET)// 3 public User getUser(@PathVariable String useName) { 4 User user = new User(); 5 user.setName(useName); 6 user.setAge(18); 7 return user; 8 }
然后在浏览器输入地址：http://localhost:8080/getUser/whh ,结果竟然报错：
报错：
Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Thu Jan 17 10:27:27 CST 2019
There was an unexpected error (type=Internal Server Error, status=500).
Missing URI template variable \'useName\' for method parameter of type String
------>网上搜了很多资料，一般这种报错都是因为：controller上的@RequestMapping的实参和方法里面的形参名字不一致，但是我的代码两个参数“userName”是一样的
然后我又试了适用别名的方法，还是不行：代码如下：
1 @RequestMapping(name = "/getUser/{userN}",method=RequestMethod.GET)// 2 public User getUser(@PathVariable("userN") @Valid String useName) { 3 User user = new User(); 4 user.setName(useName); 5 user.setAge(18); 6 return user; 7 }
---->最后终于找到了原因：竟是因为RequestMapping的参数问题:不小心把value写成了name。 改成value后，浏览器页面返回：
{"name":"whh","age":18,"pass":null}
查看下面源码可知：name:Assign a name to this mapping.(给这个mapping分配一个名称)，没有实质性的作用;
类似于注释，对程序没什么影响，但是对人友好，因为有些url是拼音的，隔了几个月没有注释的话可能不知道这个url干吗的
所以，RequestMapping地址进行映射：只能用value或path,不能使用name.
1 @Target({ElementType.METHOD, ElementType.TYPE}) 2 @Retention(RetentionPolicy.RUNTIME) 3 @Documented 4 @Mapping 5 public @interface RequestMapping { 6 7 /** 8 * Assign a name to this mapping. 9 * <p><b>Supported at the type level as well as at the method level!</b> 10 * When used on both levels, a combined name is derived by concatenation 11 * with "#" as separator. 12 * @see org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder 13 * @see org.springframework.web.servlet.handler.HandlerMethodMappingNamingStrategy 14 */ 15 String name() default ""; 16 17 /** 18 * The primary mapping expressed by this annotation. 19 * <p>In a Servlet environment this is an alias for {@link #path}. 20 * For example {@code @RequestMapping("/foo")} is equivalent to 21 * {@code @RequestMapping(path="/foo")}. 22 * <p>In a Portlet environment this is the mapped portlet modes 23 * (i.e. "EDIT", "VIEW", "HELP" or any custom modes). 24 * <p><b>Supported at the type level as well as at the method level!</b> 25 * When used at the type level, all method-level mappings inherit 26 * this primary mapping, narrowing it for a specific handler method. 27 */ 28 @AliasFor("path") 29 String[] value() default {}; 30 31 /** 32 * In a Servlet environment only: the path mapping URIs (e.g. "/myPath.do"). 33 * Ant-style path patterns are also supported (e.g. "/myPath/*.do"). 34 * At the method level, relative paths (e.g. "edit.do") are supported 35 * within the primary mapping expressed at the type level. 36 * Path mapping URIs may contain placeholders (e.g. "/${connect}"). 37 * <p><b>Supported at the type level as well as at the method level!</b> 38 * When used at the type level, all method-level mappings inherit 39 * this primary mapping, narrowing it for a specific handler method. 40 * @see org.springframework.web.bind.annotation.ValueConstants#DEFAULT_NONE 41 * @since 4.2 42 */ 43 @AliasFor("value") 44 String[] path() default {}; 45 46 /** 47 * The HTTP request methods to map to, narrowing the primary mapping: 48 * GET, POST, HEAD, OPTIONS, PUT, PATCH, DELETE, TRACE. 49 * <p><b>Supported at the type level as well as at the method level!</b> 50 * When used at the type level, all method-level mappings inherit 51 * this HTTP method restriction (i.e. the type-level restriction 52 * gets checked before the handler method is even resolved). 53 * <p>Supported for Servlet environments as well as Portlet 2.0 environments. 54 */ 55 RequestMethod[] method() default {}; 56 57 58 59 }
9.参数校验依赖于hibernate-validator：见下图
SpringBoot使用:@Valid（package javax.validation;属于validation-api-1.1.0.Final.jar）+BindingResult进行参数校验：代码如下:
User类：
1 package com.yst.helloWorld.domain; 2 3 import javax.validation.constraints.Max; 4 import javax.validation.constraints.Min; 5 6 import org.hibernate.validator.constraints.Length; 7 import org.hibernate.validator.constraints.NotEmpty; 8 9 public class User { 10 @NotEmpty(message="姓名不能为空") 11 private String name; 12 @Max(value=100,message="年龄不能大于 100 岁") 13 @Min(value=18,message="必须年满 18 岁") 14 private int age; 15 @NotEmpty(message="密码不能为空|") 16 @Length(min=6,message="密码长度不能小于6位") 17 private String pass; 18 //... 19 20 21 }
controller方法：
1 /** 2 * 参数校验@Valid+BindingResult 3 * 打印错误信息 4 * @param user 5 * @param result 6 */ 7 @RequestMapping("/saveUser") 8 public void saveUser(@Valid User user,BindingResult result) { 9 System.out.println("user:"+user); 10 if(result.hasErrors()) { 11 List<ObjectError> list = result.getAllErrors(); 12 for (ObjectError error : list) { 13 System.out.println(error.getCode()+"-"+error.getDefaultMessage()); 14 } 15 } 16 }
测试方法：
1 @Test 2 public void saveUser() throws Exception { 3 mockMvc.perform(MockMvcRequestBuilders.post("/saveUser")//请求的url,请求的方法是post 4 .param("name", "")//添加参数 5 .param("age", "222")//添加参数 6 .param("pass", "123")//添加参数 7 ).andDo(new ResultHandler() { 8 @Override 9 public void handle(MvcResult result) throws Exception { 10 System.out.println("结果："+result.getResponse().getContentAsString()); 11 System.out.println("请求状态码："+result.getResponse().getStatus()); 12 } 13 }); 14 }
结果返回：
user:com.yst.helloWorld.domain.User@119cbf96
Max-年龄不能大于 100 岁
NotEmpty-姓名不能为空
Length-密码长度不能小于6位
结果显示已经触发了校验规则，返回了错误信息。实际项目开发中可以对错误信息进行包装，返回前端页面展示。
10.自定义资源文件Property:代码如下
application.properties：
1 #application.properties 2 com.whh.title=whh 3 com.whh.description=分享技术和生活
自定义配置类：
1 package com.yst.helloWorld.domain; 2 3 import org.springframework.beans.factory.annotation.Value; 4 import org.springframework.stereotype.Component; 5 @Component 6 public class WhhProperties { 7 @Value("${com.whh.title}") 8 private String title; 9 @Value("${com.whh.description}") 10 private String description; 11 public String getTitle() { 12 return title; 13 } 14 public void setTitle(String title) { 15 this.title = title; 16 } 17 public String getDescription() { 18 return description; 19 } 20 public void setDescription(String description) { 21 this.description = description; 22 } 23 24 25 26 }
单元测试代码：
1 package com.yst.helloWorld; 2 3 import javax.annotation.Resource; 4 5 import org.junit.Test; 6 import org.junit.runner.RunWith; 7 import org.springframework.boot.test.context.SpringBootTest; 8 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; 9 import org.springframework.test.context.junit4.SpringRunner; 10 import com.yst.helloWorld.domain.WhhProperties; 11 //@RunWith:运行器，让测试运行于Spring环境; 12 //@RunWith(SpringRunner.class)=@RunWith(SpringJUnit4ClassRunnerRunner.class);SpringRunner extends SpringJUnit4ClassRunner 13 @RunWith(SpringRunner.class) 14 @SpringBootTest 15 public class PropertiesTest { 16 @Resource 17 private WhhProperties whhProperties; 18 19 @Test 20 public void testProperties() throws Exception { 21 System.out.println("title:"+whhProperties.getTitle()); 22 System.out.println("description:"+whhProperties.getDescription()); 23 } 24 25 }
运行结果：
title:whh
description:å享ææ¯åçæ´»
------》出现中文乱码，暂时未解决
11.Spring Data Jpa数据库连接：
（1）添加依赖：
1 <!--jpa的jar包 ，操作数据库的，类似hibernate--> 2 <dependency> 3 <groupId>org.springframework.boot</groupId> 4 <artifactId>spring-boot-starter-data-jpa</artifactId> 5 </dependency> 6 <!-- 由于Oracle授权问题，Maven不提供Oracle JDBC driver， spring boot用ide新建项目遇到的restcontroller不能导入的问题