1. 简介

拦截器（Interceptor）是一种动态拦截方法调用的机制。

作用：

在指定的方法调用前后执行预先设定后的代码。
阻止原始方法的执行。

拦截器与过滤器的区别

归属不同：Filter属于Servlet技术，Interceptor属于SpringMVC技术
拦截内容不同：Filter对所有访问进行增强，Interceptor仅针对SpringMVC的访问进行增强。

2.入门案例

制作拦截器功能类
src/main/java/org/example/controller/interceptor/ProjectInterceptor.java

package org.example.controller.interceptor;

import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

@Component
public class ProjectInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...");
        return true;
        // return false; // 用来终止原始操作
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }
}

配置拦截器的执行位置

src/main/java/org/example/config/SpringMvcConfig.java

package org.example.config;

import org.example.controller.interceptor.ProjectInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
@ComponentScan({"org.example.controller"})
@EnableWebMvc
public class SpringMvcConfig implements WebMvcConfigurer {
    @Autowired
    private ProjectInterceptor projectInterceptor;

    // 配置拦截器
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(projectInterceptor).addPathPatterns("/books", "/books/*");
    }
}

src/main/java/org/example/config/ServletConfig.java

package org.example.config;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

public class ServletConfig extends AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class[0];
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{SpringMvcConfig.class};
    }

    @Override
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }
}

src/main/java/org/example/controller/BookController.java

package org.example.controller;

import org.example.domain.Book;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/books")
public class BookController {

    @PostMapping
    public String save(@RequestBody Book book) {
        System.out.println("book save..." + book);
        return "{'module':'book save'}";
    }

    @PutMapping
    public String update(@RequestBody Book book) {
        System.out.println("book save..." + book);
        return "{'module':'book update'}";
    }

    @DeleteMapping("/{id}")
    public String delete(@PathVariable Integer id) {
        System.out.println("book save..." + id);
        return "{'module':'book delete'}";
    }

    @GetMapping("/{id}")
    public String getById(@PathVariable Integer id) {
        System.out.println("book getById..." + id);
        return "{'module':'book getById'}";
    }

    @GetMapping
    public String getAll() {
        System.out.println("book getAll...");
        return "{'module':'book getAll'}";
    }
}

src/main/java/org/example/domain/Book.java

package org.example.domain;

public class Book {
    private Integer id;
    private String type;
    private String name;
    private String description;

    @Override
    public String toString() {
        return "Book{" +
                "id=" + id +
                ", type='" + type + '\'' +
                ", name='" + name + '\'' +
                ", description='" + description + '\'' +
                '}';
    }

    public Integer getId() {
        return id;
    }

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

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getName() {
        return name;
    }

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

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }
}

配置Tomcat，并运行。发送Post请求：http://localhost:8080/books。控制台输出如下：