什么是拦截器

DispatcherServlet收到请求之后，如果有拦截器，则先执行拦截器的方法，再执行处理器(Controller)的方法
过滤器属于Servlet规范，拦截的是Servlet容器调用过程
而拦截器属于Spring框架，拦截的是DispatcherServlet的调用过程

如何写拦截器

写一个java类，实现HandlerInterceptor接口
在接口方法当中，实现拦截处理逻辑
配置拦截器

添加jar包依赖

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>cn.company</groupId>
	<artifactId>TestDemo</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>
	<dependencies>
		<!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>5.2.5.RELEASE</version>
		</dependency>
		<!-- servlet的jar包依赖, <scope>provided</scope> 表示编译时有效，不会打包发布到Tomcat中 -->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>javax.servlet-api</artifactId>
			<version>4.0.1</version>
			<scope>provided</scope>
		</dependency>
		<!-- jsp的jar包依赖 -->
		<dependency>
			<groupId>javax.servlet.jsp</groupId>
			<artifactId>javax.servlet.jsp-api</artifactId>
			<version>2.3.3</version>
			<scope>provided</scope>
		</dependency>
		<!-- jstl表达式 -->
		<!-- https://mvnrepository.com/artifact/jstl/jstl -->
		<dependency>
			<groupId>jstl</groupId>
			<artifactId>jstl</artifactId>
			<version>1.2</version>
		</dependency>
	</dependencies>
	<!-- 添加tomcat插件 -->
	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.tomcat.maven</groupId>
				<artifactId>tomcat7-maven-plugin</artifactId>
				<version>2.2</version>
				<configuration>
					<port>8080</port>
					<hostName>localhost</hostName>
					<uriEncoding>UTF-8</uriEncoding>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

配置前端控制器

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
  <display-name>TestDemo</display-name>
  <servlet>
  	<servlet-name>springmvc</servlet-name>
  	<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  	<init-param>
  		<param-name>contextConfigLocation</param-name>
  		<param-value>classpath:spring-mvc.xml</param-value>
  	</init-param>
  	<load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
  	<servlet-name>springmvc</servlet-name>
  	<url-pattern>/</url-pattern>
  </servlet-mapping>
</web-app>

Controller的编写

package controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class HelloController {
    
    
	@RequestMapping("/hello")
	public String hello() {
    
    
		System.out.println("hello()");
		return "hello";
	}
	@RequestMapping("/demo/hello2")
	public String hello2() {
    
    
		System.out.println("hello2()");
		return "hello";
	}
}

hello.jsp

<%@ page contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>hello</title>
</head>
<body style="font-size:30px;">
	Hello Kitty
</body>
</html>

编写拦截器

1、先调用preHandle，返回true继续向后执行，返回false中断请求
2、调用Controller(处理器）返回ModelAndView给前端控制器之前调用postHandle
3、请求处理完毕，最后调用afterCompletion

package inceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

public class SomeInceptor implements HandlerInterceptor {
    
    
	/*
	 * DispatcherServlet在收到请求之后，
	 * 会先调用 拦截器的preHandle方法。
	 *  如果该方法的返回值是true,是继续向后执行；
	 * 如果该方法的返回值是false,
	 * 则中断请求，返回结果。
	 *  handler:处理器方法对象
	 */
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {
    
    
		System.out.println("preHandle()");
		return true;
	}
	/*
	 * 处理器(Controller)的方法执行完毕，正准备将
	 * 处理结果(ModelAndView)返回给DispatcherServlet
	 * 之前，执行postHandle方法。
	 * 注：
	 * 	可以在该方法里面，修改处理结果(ModelAndView)。
	 */
	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
			ModelAndView modelAndView) throws Exception {
    
    
		System.out.println("postHandle()");
	}
	/*
	 *整个请求处理完毕，最后执行的方法。
	 *ex:处理器方法所抛出的异常
	 */
	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
			throws Exception {
    
    
		System.out.println("afterCompletion()");
	}
}

配置拦截器

在springmvc的配置文件中配置拦截器

<?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:context="http://www.springframework.org/schema/context"
	xmlns:jdbc="http://www.springframework.org/schema/jdbc"
	xmlns:jee="http://www.springframework.org/schema/jee"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:aop="http://www.springframework.org/schema/aop"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xmlns:util="http://www.springframework.org/schema/util"
	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-3.2.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
		http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
		http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
		http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
		http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
		http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd">

<!-- 配置组件扫描 -->
	<context:component-scan base-package="controller" />
	<!-- 配置MVC注解扫描  --> 
	<mvc:annotation-driven />
	<!-- 配置视图解析器 -->
	<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="prefix" value="/WEB-INF/" />
		<property name="suffix" value=".jsp" />
	</bean>
	<!--静态资源的加载  -->
	<mvc:resources location="/" mapping="/**" />
	<!-- 配置springmvc的拦截器 -->
	<mvc:interceptors>
		<mvc:interceptor>
			<mvc:mapping path="/**"/>
			<bean class="inceptor.SomeInceptor"/>
		</mvc:interceptor>
	</mvc:interceptors>
</beans>

页面访问

在这里插入图片描述
控制台输出

拦截器的优先级

依据配置的先后顺序执行。

SpringMVC中的异常处理

可以将异常抛给Spring框架，由Spring框架来处理异常

配置简单异常处理器

在springmvc的配置文件中添加配置如下

<!-- 配置简单异常处理器 -->
	<bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
		<property name="exceptionMappings">
			<props>
				<!--java.lang.NumberFormatException:异常类型, erro1:视图页面 -->
				<prop key="java.lang.NumberFormatException">erro1</prop>
			</props>
		</property>
	</bean>

添加异常处理页面：jsp页面

<%@ page contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body style="font-size:30px;">
			请输入正确的数字
</body>
</html>

3、控制器的编写

package controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class HelloController {
    
    
	@RequestMapping("/hello")
	public String hello() {
    
    
		System.out.println("hello()");
		Integer.parseInt("123a");
		return "hello";
	}
}

4、页面访问
http://localhost:8080/TestDemo/hello
在这里插入图片描述

@ExceptionHandler注解

在处理器类里面增加一个异常处理方法，该方法前面需要添加@ExceptionHandler
Spring框架捕获到异常之后，会调用异常处理方法
在异常处理方法里面，编写异常处理逻辑
添加异常处理页面

增加一个异常处理方法

package controller;

import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class HelloController {
    
    
	@RequestMapping("/hello")
	public String hello() {
    
    
		System.out.println("hello()");
		Integer.parseInt("123a");
		return "hello";
	}
	@RequestMapping("/hello2")
	public String hello2() {
    
    
		System.out.println("hello2()");
		"1234".charAt(8);
		return "hello";
	}
	/*
	 * e:处理器方法所抛出的异常
	 */
	@ExceptionHandler
	public String handleEx(Exception e,HttpServletRequest request) {
    
    
		System.out.println("handleEx()");
		if(e instanceof NumberFormatException) {
    
    
			request.setAttribute("msg","请输入合法的数字");
			return "error3";
		}
		if(e instanceof StringIndexOutOfBoundsException) {
    
    
			request.setAttribute("msg","下标越界啦");
			return "error3";
		}
		//其他异常
		return "error";
	}
}

添加异常处理页面

error.jsp

<%@page pageEncoding="utf-8" 
contentType="text/html; charset=utf-8" %>
<html>
	<head></head>
	<body style="font-size:30px;">
		系统繁忙，稍后重试
	</body>
</html>

error3.jsp

<%@page pageEncoding="utf-8" 
contentType="text/html; charset=utf-8" %>
<html>
	<head></head>
	<body style="font-size:30px;">
		${msg}
	</body>
</html>

页面访问
在这里插入图片描述

配有拦截器的调用过程

在这里插入图片描述

SpringJdbc

什么是SpringJdbc

Spring框架对jdbc的封装。
注：比起直接使用jdbc，使用SpringJdbc代码更简洁，质量更高。
比如，不用考虑获取连接与关闭连接等操作。

如何使用

1、导包

spring-webmvc,spring-jdbc,mysql,dbcp,junit

<!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>5.2.5.RELEASE</version>
		</dependency>
		<!--springjdbc的jar包依赖 -->
		<!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-jdbc</artifactId>
			<version>5.2.5.RELEASE</version>
		</dependency>
		<!--mysql -->
		<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>8.0.19</version>
		</dependency>
		<!--数据库连接池，dbcp  -->
		<!-- https://mvnrepository.com/artifact/commons-dbcp/commons-dbcp -->
		<dependency>
			<groupId>commons-dbcp</groupId>
			<artifactId>commons-dbcp</artifactId>
			<version>1.4</version>
		</dependency>
		<!--junit：单元测试  -->
		<!-- https://mvnrepository.com/artifact/junit/junit -->
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.12</version>
			<scope>test</scope>
		</dependency>

2、添加Spring配置文件

配置JdbcTemplate

<?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:context="http://www.springframework.org/schema/context" 
	xmlns:jdbc="http://www.springframework.org/schema/jdbc"  
	xmlns:jee="http://www.springframework.org/schema/jee" 
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:aop="http://www.springframework.org/schema/aop" 
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xmlns:util="http://www.springframework.org/schema/util"
	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-3.2.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
		http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
		http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
		http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
		http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
		http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd">
		
		
	<!-- 配置数据库连接池 -->	
	<util:properties location="classpath:db.properties" id="db"/>
	<bean id="ds" class="org.apache.commons.dbcp.BasicDataSource">
		<property name="driverClassName" value="#{db['jdbc.driver']}"/>
		<property name="url" value="#{db['jdbc.url']}"/>
		<property name="username" value="#{db['jdbc.username']}"/>
		<property name="password" value="#{db['jdbc.password']}"/>
	</bean>
	<!-- 配置组件扫描 -->
	<context:component-scan base-package="dao"/>
	<!-- 配置JdbcTemplate -->
	<bean class="org.springframework.jdbc.core.JdbcTemplate" id="jt">
		<property name="dataSource" ref="ds"/>
	</bean>
</beans>

3、添加entity和dao(持久层)

package entity;

public class Employee {
    
    
	private int id;
	private String ename;
	private double salary;
	private int age;

	public int getId() {
    
    
		return id;
	}

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

	public String getEname() {
    
    
		return ename;
	}

	public void setEname(String ename) {
    
    
		this.ename = ename;
	}

	public double getSalary() {
    
    
		return salary;
	}

	public void setSalary(double salary) {
    
    
		this.salary = salary;
	}

	public int getAge() {
    
    
		return age;
	}

	public void setAge(int age) {
    
    
		this.age = age;
	}

	public String toString() {
    
    
		return "Employee [id=" + id + ", ename=" + ename + ", salary=" + salary + ", age=" + age + "]";
	}
}

调用JdbcTemplate提供的方法来访问数据库,通常将JdbcTemplate注入到DAO

package dao;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.dao.EmptyResultDataAccessException;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Repository;

import entity.Employee;

@Repository("employeeDAO")
public class EmployeeDAO {
    
    
	@Autowired
	@Qualifier("jt")
	JdbcTemplate jt;
	/*
	 *新增数据
	 */
	public void save(Employee e){
    
    
		String sql="insert into t_emp values(null,?,?,?)";
		//数组元素应该与?一一对应
		Object[]args= {
    
    
			e.getEname(),e.getSalary(),e.getAge()	
		};
		jt.update(sql,args);
	}
	/*
	 *查询所有数据
	 */
	public List<Employee>findAll(){
    
    
		String sql="select * from t_emp";
		List<Employee>employees=jt.query(sql, new EmpRowMapper());
		return employees;
	}
	/*
	 *根据id查询
	 */
	public Employee findById(int id) {
    
    
		String sql="select * from t_emp where id=?";
		Object[]args= {
    
    id};
		Employee e=null;
		try {
    
    
			e=jt.queryForObject(sql, args, new EmpRowMapper());
		}catch(EmptyResultDataAccessException e1) {
    
    
			/*
			 * 找不到对应的记录，queryForObject方法。
			 * 会抛出EmptyResultDataAccessException
			 */
			return null;
		}
		
		return e;
	}
	/*
	 *更新数据
	 */
	public void update(Employee e) {
    
    
		String sql="update t_emp set ename=?,salary=?,age=? where id=?";
		Object[]args= {
    
    
			e.getEname(),e.getSalary(),e.getAge(),e.getId()	
		};
		jt.update(sql, args);
	}
	/*
	 *根据id删除数据
	 */
	public void delete(int id) {
    
    
		String sql="delete from t_emp where id=?";
		Object[]args= {
    
    id};
		jt.update(sql, args);
	}
	/**
	 * 负责高速JdbcTemplate如何将记录转换成一个对象,
	 * rowNum:正在被处理的记录的下标
	 */
	class EmpRowMapper implements RowMapper<Employee>{
    
    

		public Employee mapRow(ResultSet rs, int rowNum) throws SQLException {
    
    
			Employee e=new Employee();
			e.setId(rs.getInt("id"));
			e.setEname(rs.getString("ename"));
			e.setSalary(rs.getDouble("salary"));
			e.setAge(rs.getInt("age"));
			return e;
		}
		
	}
}

测试程序

package test;

import java.util.List;

import org.junit.Before;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import dao.EmployeeDAO;
import entity.Employee;

public class TestCase {
    
    
	EmployeeDAO dao;
	//junit在执行测试方法前，会先执行@Before修饰的方法
	@Before
	public void before() {
    
    
		String config = "spring-jdbc.xml";
		ApplicationContext ac = new ClassPathXmlApplicationContext(config);
		dao = ac.getBean("employeeDAO", EmployeeDAO.class);
	}

	@Test
	public void save() {
    
    
		Employee e = new Employee();
		e.setEname("小月");
		e.setSalary(20000);
		e.setAge(22);
		dao.save(e);
	}

	@Test
	public void findAll() {
    
    
		List<Employee> employees = dao.findAll();
		for (Employee employee : employees) {
    
    
			System.out.println(employee);
		}
	}
	@Test
	public void findById() {
    
    
		Employee e=dao.findById(3);
		System.out.println(e);
	}
	@Test
	public void update() {
    
    
		Employee e=dao.findById(3);
		e.setAge(e.getAge()+10);
		e.setSalary(e.getSalary()*2);
		dao.update(e);
	}
	@Test
	public void delete() {
    
    
		dao.delete(3);
	}
}

拦截器、异常处理器、springjdbc

拦截器和springmvc异常处理、springjdbc