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@ControllerAdvice的使用
|JavaSpringboot
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处理全局异常

我们使用fileupload项目来进行测试，首先我们设置上传文件的大小限制

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spring.servlet.multipart.max-file-size=1KB

测试一下，我们可以看到出现了FileSizeLimitExceededException，同时还有一个提示信息This application has no explicit mapping for /error, so you are seeing this as a fallback. 那么我们如何自定义一个错误提示呢？我们创建一个MyException类

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package com.example.fileupload;

import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.multipart.MaxUploadSizeExceededException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

/**
 * @author: WJZheng
 * @date: 2020/3/16 16:31
 * @description:
 */
@ControllerAdvice
public class MyException {

    @ExceptionHandler(MaxUploadSizeExceededException.class)
    public void myException(MaxUploadSizeExceededException e, HttpServletResponse response) throws IOException {
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        writer.write("上传文件大小超出限制");
        writer.flush();
        writer.close();
    }
}

我们再来做一次文件上传，我们可以看到自定义的错误提示了

那么如果我们想自定义一个错误页面呢？首先我们添加thymeleaf依赖，然后添加一个方法

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package com.example.fileupload;

import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

/**
 * @author: WJZheng
 * @date: 2020/3/16 16:31
 * @description:
 */
@ControllerAdvice
public class MyException {

//    @ExceptionHandler(MaxUploadSizeExceededException.class)
//    public void myException(MaxUploadSizeExceededException e, HttpServletResponse response) throws IOException {
//        response.setContentType("text/html;charset=utf-8");
//        PrintWriter writer = response.getWriter();
//        writer.write("上传文件大小超出限制");
//        writer.flush();
//        writer.close();
//    }

    @ExceptionHandler(MaxUploadSizeExceededException.class)
    public ModelAndView myException(MaxUploadSizeExceededException e) throws IOException {
        ModelAndView modelAndView = new ModelAndView("error");
        modelAndView.addObject("error","上传文件大小超出限制");
        return modelAndView;
    }
}

然后在template目录下创建一个error.html文件

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<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <h1 th:text="${error}"></h1>
</body>
</html>

上传一个超出1KB的文件后就会看到自定义的错误提示页面了

预设全局数据

我们先创建一个GlobalData类，该类定义了一个全局数据，即任意一个Controller都可以获取到

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package com.example.controlleradvice;

import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ModelAttribute;

import java.util.HashMap;
import java.util.Map;

/**
 * @author: WJZheng
 * @date: 2020/3/16 16:48
 * @description:
 */

@ControllerAdvice
public class GlobalData {
    
    //这里的key就是info，value就是该方法的返回值
    @ModelAttribute(value = "info")
    public Map<String,Object> myData() {
        Map<String, Object> map = new HashMap<>();
        map.put("name","WJZheng");
        map.put("address","https://wellenzheng.github.io/");
        return map;
    }
}

然后我们创建一个Controller，通过Model来获取数据并在控制台输出

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package com.example.controlleradvice;

import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.Map;
import java.util.Set;

/**
 * @author: WJZheng
 * @date: 2020/3/16 16:51
 * @description:
 */

@RestController
public class DataController {
    @GetMapping("/data")
    public String data(Model model) {
        Map<String, Object> map = model.asMap();
        Set<String> keySet = map.keySet();
        for (String key : keySet) {
            System.out.println(key + ":" + map.get(key));
        }
        return "data";
    }
}

请求参数预处理

我们首先创建一个Book类和一个Author类，他们都有一个同名的属性name。

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package com.example.controlleradvice;

/**
 * @author: WJZheng
 * @date: 2020/3/16 17:04
 * @description:
 */
public class Book {
    private String id;
    private String name;
    private Double price;

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

    public String getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public Double getPrice() {
        return price;
    }

    public void setPrice(Double price) {
        this.price = price;
    }
}
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package com.example.controlleradvice;

/**
 * @author: WJZheng
 * @date: 2020/3/16 17:05
 * @description:
 */
public class Author {
    private String name;
    private Integer age;

    @Override
    public String toString() {
        return "Author{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

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

然后在Controller里添加一个方法来post数据

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package com.example.controlleradvice;

import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author: WJZheng
 * @date: 2020/3/16 17:05
 * @description:
 */

@RestController
public class BookController {
    @PostMapping("/book")
    public void addBook(@ModelAttribute("book") Book book, @ModelAttribute("author") Author author){ //@ModelAttribute是为参数创建一个别名
        System.out.println(book);
        System.out.println(author);
    }
}

最后在GlobalData中为这两个参数绑定一个前缀

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package com.example.controlleradvice;

import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.InitBinder;
import org.springframework.web.bind.annotation.ModelAttribute;

import java.util.HashMap;
import java.util.Map;

/**
 * @author: WJZheng
 * @date: 2020/3/16 16:48
 * @description:
 */

@ControllerAdvice
public class GlobalData {

    @InitBinder("author")
    public void initAuthor(WebDataBinder binder){
        binder.setFieldDefaultPrefix("a.");
    }

    @InitBinder("book")
    public void initBook(WebDataBinder binder){
        binder.setFieldDefaultPrefix("b.");
    }
}

然后在postman中进行测试，我们就可以在提交的数据中加上前缀来区别这两个类的同名属性

若未加预处理之前，springboot会把两个同名属性合并在一起

Author: WJZheng
Link: https://wellenzheng.github.io/2020/03/16/ControllerAdvice%E7%9A%84%E4%BD%BF%E7%94%A8/
Copyright Notice: All articles in this blog are licensed under CC BY-NC-SA 4.0 unless stating additionally.
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