Spring Boot 总是返回 404 错误答案

【问题标题】：Spring boot always returns a 404 errorSpring Boot 总是返回 404 错误
【发布时间】：2018-07-15 07:02:33
【问题描述】：

我正在尝试让 Spring Boot (1.5.9) 项目以简单的 Hello world 消息进行响应。但是，我发送的任何请求都会立即返回 404 异常。

MyBackendApplication

package net.mypackage.backend;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class MyBackendApplication {

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

控制器/HelloController

package net.mypackage.backend.controllers;

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;

@RestController
public class HelloController {

    @RequestMapping("/hello")
    public String sayHello() {
        return "Hello, world!";
    }

}

application.properties

server.port = 5000
server.contextPath=/
logging.level.org=DEBUG

build.gradle

buildscript {
    ext {
        springBootVersion = '1.5.9.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'

group = 'net.mypackage'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8

repositories {
    mavenCentral()
}


dependencies {
    compile('org.springframework.boot:spring-boot-starter-jersey')
    runtime('org.springframework.boot:spring-boot-devtools')
    testCompile('org.springframework.boot:spring-boot-starter-test')
    compile("org.springframework.boot:spring-boot-starter-actuator")
}

请求页面 (localhost:5000/hello) 时，我收到 404 错误。以下信息显示在此请求的日志中（here 是一个要点，因为我不喜欢将其格式化为引号的方式）：

2018-02-05 13:01:37.600 调试 17448 --- [nio-5000-exec-2] o.a.coyote.http11.Http11InputBuffer : 收到 [GET / HTTP/1.1
缓存控制：无缓存用户代理：PostmanRuntime/7.1.1 接受： / 主机：127.0.0.1:5000 接受编码：gzip，放气连接：保持活动] 2018-02-05 13:01:37.601 调试 17448 --- [nio-5000-exec-2] o.a.c.authenticator.AuthenticatorBase：安全检查请求 GET / 2018-02-05 13:01:37.601 DEBUG 17448 --- [nio-5000-exec-2] org.apache.catalina.realm.RealmBase：没有定义适用的约束 2018-02-05 13:01:37.601 DEBUG 17448 --- [nio-5000-exec-2] o.a.c.authenticator.AuthenticatorBase：不受任何约束 2018-02-05 13:01:37.604 DEBUG 17448 --- [nio-5000-exec-2] o.a.tomcat.util.net.SocketWrapperBase：套接字： [org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper@4bfc0a6:org.apache.tomcat.util.net.NioChannel@b945368:java.nio.channels.SocketChannel[已连接本地=/127.0.0.1:5000 远程=/127.0.0.1:53684]]，从缓冲区读取：[0] 2018-02-05 13:01:37.604 调试 17448 --- [nio-5000-exec-2] o.apache.coyote.http11.Http11Processor：套接字： [org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper@4bfc0a6:org.apache.tomcat.util.net.NioChannel@b945368:java.nio.channels.SocketChannel[已连接本地=/127.0.0.1:5000 远程=/127.0.0.1:53684]]，状态： [OPEN_READ]，说明：[OPEN]

我确定我错过了一些非常基本的东西，但我终其一生都无法弄清楚是什么。在此先感谢:)

【问题讨论】：

首先，如果您不想保留上下文路径，请从那里删除server.contextPath。默认情况下它会在ip:port
@user3145373ツ谢谢，我在别处看到建议添加/ 的上下文路径。我从我的应用程序配置中删除了它，但仍然有同样的问题。
能否列出 pom.xml 配置和依赖项。
从日志看来它正在寻找 / 而不是 /hello - Security checking request GET /
修复你的 gradle 依赖。它应该有compile("org.springframework.boot:spring-boot-starter-web")，实际上只是尝试：dependencies {compile("org.springframework.boot:spring-boot-starter-web")}

标签： java spring-boot

【解决方案1】：

您提供的信息不够。

当我用这个 pom.xml 尝试你的应用程序和控制器时：

<?xml version="1.0" encoding="UTF-8"?>
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>mvc</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>MVC</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

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

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

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

它适用于server.contextPath=/，也适用于注释掉。

【讨论】：

【解决方案2】：

此代码适用于我，除了以下代码之外没有单个字符可以运行 Spring Boot 简单 API。我认为您的应用程序中存在一些配置类或 pom 问题。

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.10.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

HelloController.java

package com.example.demo;

import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.bind.annotation.RequestMapping;

@RestController
public class HelloController {

    @RequestMapping("/hello")
    public String sayHello() {
        return "Hello, world!";
    }
}

DemoApplication.java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

application.properties

server.port = 5000
logging.level.org=DEBUG

运行成功

【讨论】：