SpringBoot简单使用(2)

1.2.7：CommandLineRunner 接口：

开发中可能会有这样的情景。需要在容器启动后执行一些内容。比如读取配置文件，数据库连接之类的。SpringBoot 给我们提供了两个接口来帮助我们实现这种需求。这两个接口分别为 CommandLineRunner 和 ApplicationRunner。他们的执行时机为容器启动完成的时候。这两个接口中有一个 run 方法，我们只需要实现这个方法即可。这两个接口的不同之处在于： ApplicationRunner 中 run 方法的参数为 ApplicationArguments ，而 CommandLineRunner 接口中 run 方法的参数为 String 数组

例子：定义接口：

public interface SomeService {
    void sayHello(String name);
}

定义实现类：

@Service("someservice")
public class SomeServiceImpl implements SomeService{

    @Override
    public void sayHello(String name) {
        System.out.println("欢迎"+name);
    }
}

继承CommandLineRunner，实现run方法

@SpringBootApplication
public class Springboot01Application implements CommandLineRunner {

    public static void main(String[] args) {

        ApplicationContext context = SpringApplication.run(Springboot01Application.class, args);
        SomeService sc =(SomeService) context.getBean("someservice");
        sc.sayHello("李四");
    }

    @Override
    public void run(String... args) throws Exception {
        System.out.println("在容器对象创建好后执行的对象");
    }
}

1.3：Spring Boot 和 web 组件

1.3.1：springboot拦截器：

Spring Boot 使用拦截器步骤： 1．创建类实现 HandlerInterceptor 接口

public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("执行了拦截器");
        return true;
    }
}

2．注册拦截器对象

@Configuration  //相当于springmvc配置文件
public class MyAppConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //指定拦截的地址
        String path[]={"/user/**"};
        //指定放行的地址
        String excludePath[]={"/user/login"};
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns(path)
                .excludePathPatterns(excludePath);
    }
}

3．创建测试使用的 Controller

@RequestMapping("/user/login")
@ResponseBody
public String userlogin(HttpServletRequest request){

    return "userlogin";
}
@RequestMapping("/user/regiest")
@ResponseBody
public String userreigest(HttpServletRequest request){

    return "userregiest";
}

4:访问浏览器并观察：执行

/user/regiest

被拦截

1.3.2：Spring Boot 中使用 Servlet

1. 创建 Servlet：

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=uft-8");
        PrintWriter writer = resp.getWriter();
        writer.print("使用servlet对象");
        writer.flush();
        writer.close();
    }
}

2. 注册 Servlet

@Configuration  
public class MyAppConfig {
    @Bean
    public ServletRegistrationBean servletRegistrationBean(){
        ServletRegistrationBean bean = new ServletRegistrationBean(new MyServlet(),"/myservlet");
        return  bean;
    }
}

3. 主启动类启动

4.启动主类，在浏览器中访问

1.3.2：Spring Boot 中使用 Filter

1.3.2.1：使用自己定义的过滤器

1.创建 Filter 对象

public class MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("使用过滤器");
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {

    }
}

2.注册 Filter

@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean registrationBean(){
        FilterRegistrationBean bean = new FilterRegistrationBean();
        bean.setFilter(new MyFilter());
        bean.addUrlPatterns("/user/*");
        return bean;
    }
}

3.创建 Controller

@Controller
public class HelloSpringBoot {

@RequestMapping("/user/login")
    @ResponseBody
    public String userlogin(){
    return "userloign";
}

}

4.启动应用，在浏览器访问

1.3.2.2 字符集过滤器的应用：

1.创建 Servlet，输出中文数据

public class MyServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html");
        PrintWriter writer = resp.getWriter();
        writer.print("使用servlet对象");
        writer.flush();
        writer.close();
    }
}

2）注册 Servlet 和 Filter

@Configuration
public class CFandServletConfig {
    @Bean
    public ServletRegistrationBean servletRegistrationBean(){
        ServletRegistrationBean bean = new ServletRegistrationBean(new MyServlet(),"/myservlet");
        return  bean;
    }
    @Bean
    public FilterRegistrationBean filterRegistrationBean(){
        FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
        CharacterEncodingFilter filter = new CharacterEncodingFilter();
        filter.setEncoding("utf-8");
        filter.setForceEncoding(true);
        filterRegistrationBean.setFilter(filter);
        filterRegistrationBean.addUrlPatterns("/*");
        return filterRegistrationBean;
    }
}

3.在 application.properties , 禁用 Spring Boot 中默认启用的过滤器

server.servlet.encoding.enabled=false

4.启动主类，运行浏览器

1.3.2.4 也可以在 application.properties 文件中设置过滤器：Spring Boot 项目默认启用了 CharacterEncodingFilter, 设置他的属性就可以（这种最简单）

server.servlet.encoding.charset=utf-8

#强制 request， response 使用 charset 他的值 utf-8

server.servlet.encoding.force=true

这样不用注册字符编码过滤器了

1.4 创建 Spring Boot 项目

pom.xml：

<dependencies>
   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
   </dependency>
   <dependency>
      <groupId>org.mybatis.spring.boot</groupId>
      <artifactId>mybatis-spring-boot-starter</artifactId>
      <version>2.2.2</version>
   </dependency>

   <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <scope>runtime</scope>
   </dependency>
   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
   </dependency>
</dependencies>

<build>

   <resources>
      <resource>
         <directory>src/main/java</directory>
         <includes>
            <include>**/*.xml</include>
         </includes>
      </resource>

配置数据源：application.properties

spring.datasource.username=root
spring.datasource.password=ztb
spring.datasource.url=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT%2B8
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver


server.port=9093

实体类

package com.ztb.pojo;

public class User {
    private int id;
    private String name;
    private String pwd;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public User() {
    }
}

创建 Dao 接口

@Mapper
public interface UserMapper {
    List<User> selectAll();
}

mapper 文件：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.ztb.mapper.UserMapper">
    <select id="selectAll" resultType="com.ztb.pojo.User">
        select * from user
    </select>

</mapper>

service 接口

public interface UserService {
    List<User> selectAll();
}

service 接口实现类

@Service
public class UserServiceImpl implements UserService{

    @Resource
    UserMapper userMapper;
    @Override
    public List<User> selectAll() {
        return userMapper.selectAll();
    }
}

controller 类

@Controller
public class UserController {
    @Resource
    UserService userService;

    @RequestMapping("/user")
    @ResponseBody
    public String selectuser(){
        List<User> list = userService.selectAll();
        for (User user : list) {
            System.out.println(user);
        }
        return "查询结果";
    }
}

启动 Application 类, 浏览器访问

1.4.1 @MapperScan：在 Dao 接口上面加入@Mapper，需要在每个接口都加入注解。当 Dao 接口多的时候不方便。可以使用如下的方式解决。

1.去掉 StudentMapper 接口的上面的@Mapper 注解

2.在主类上面加入 @MapperScan()

@SpringBootApplication
@MapperScan(basePackages = "com.ztb.mapper")
public class Springboot02Application {

   public static void main(String[] args) {
      SpringApplication.run(Springboot02Application.class, args);
   }

}

1.4.2 mapper 文件和 java 代码分开管理：

mapper 文件放在 resources 目录下， java 代码放在 src/main/java。

实现步骤：在 resources 创建自定义目录，例如 mapper，存放 xml 文件

把原来的 xml 文件剪切并拷贝到 resources/mapper 目录

在 application.properties 配置文件中指定映射文件的位置，这个配置只有接口和映射文件不在同一个包的情况下，才需要指定。

mybatis.mapper-locations=classpath:mapper/*.xml
mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl

1.4.3事务支持：

Spring Boot 使用事务非常简单，底层依然采用的是 Spring 本身提供的事务管理

➢ 在入口类中使用注解 @EnableTransactionManagement 开启事务支持

➢ 在访问数据库的 Service 方法上添加注解 @Transactional 即可

步骤：修改 StudentService，在 addStudent()方法中抛出异常

@Override
@Transactional
public int adduser(User user) {
    int i = userMapper.adduser(user);
    int s=1/0;
    return i;
}

在 Application 主类上，@EnableTransactionManagement 开启事务支持 @EnableTransactionManagement 可选，但是@Service 必须添加事务才生效

@SpringBootApplication
@MapperScan(basePackages = "com.ztb.mapper")
@EnableTransactionManagement
public class Springboot02Application {

   public static void main(String[] args) {
      SpringApplication.run(Springboot02Application.class, args);
   }

}

测试应用，数据没有添加成功

注释掉 StudentServiceImpl 上的@Transactional 测试。数据添加成功

posted @ 2022-09-01 21:28 Sunward阳阅读(56) 评论(0) 收藏举报

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SpringBoot简单使用(2)

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