springboot项目图片上传到本地tomcat图片服务器
本地tomcat图片服务器
在host节点下增加节点
<Context docBase="D://picture" path="/picture" />


docBase：为图片保存的路径
path：为项目访问路径（http://localhost:8081/picture/）
修改tomcat安装目录conf下的web.xml文件,servlet（default）节点下的listings的value改为true

path：为项目访问路径（http://localhost:8081/picture/）

修改tomcat安装目录conf下的web.xml文件

servlet（default）节点下的listings的value改为true


controller层
package com.example.doublecontrol.utils;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

@Controller
@CrossOrigin
public class PictureUpload {

    @Value("${static.url}")
    private String staticUrl;//D://picture（本地图片保存地址）
    @Value("${static.addressurl}")
    private String addressurl;//http://localhost:8081/picture/（本地tomcat访问地址）

    @RequestMapping("uploadimg")
    @ResponseBody
    public Map<String, Object> upload(MultipartFile file) {
        Map<String, Object> map = new HashMap();
        Map<String, Object> map2 = new HashMap();
        String realPath = staticUrl + "//" + file.getOriginalFilename();
        File dest = new File(realPath);
        try {
            if(!dest.getParentFile().exists()){
                dest.getParentFile().mkdir();
            }
            try {
                //保存文件
                file.transferTo(dest);
            } catch (IllegalStateException e) {
                // TODO Auto-generated catch block
                System.out.println(e);
                e.printStackTrace();
            }
            String resUrl = this.addressurl+file.getOriginalFilename();//前台获取图片的地址
            map.put("code", 0);
            map.put("msg", "上传成功");
            map2.put("src", resUrl);
            map2.put("title", file.getOriginalFilename());
            map.put("data", map2);
        }catch (Exception e){
            System.out.println(e);
            map.put("code", 1);
            map.put("msg", e);
            map2.put("src", "");
            map2.put("title","");
            map2.put("data", "");
        }
        return map;
    }

    @RequestMapping("/Picturetest")
    public String login() {
        return "Welcome to picture server.";
    }
}

Java访问Tomcat图片资源
环境
CentOS Linux release 8.1.1911 (Core)
java 14.0.2 2020-07-14
Java(TM) SE Runtime Environment (build 14.0.2+12-46)
Java HotSpot(TM) 64-Bit Server VM (build 14.0.2+12-46, mixed mode, sharing)
apache-tomcat-9.0.38

实现代码
读取Tomcat主目录下./webapps/ROOT目录下默认存在的图片tomcat.png
其中，<host_name>为服务器主机名（IP地址），PORT为端口号，Tomcat默认使用8080，使用阿里云、腾讯云等服务器需要在安全组配置中设置内网入方向规则
package com.demo.tomcat;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class Tomcat {
    private static String HOST_NAME = "http://<host name>";
    private static int PORT = 8080;


    public void getImage(String filePath) {
        String path = String.format(HOST_NAME + ":%d/", PORT) + filePath;

        URL url = null;
        try {
            url = new URL(path);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("GET");

            httpURLConnection.setConnectTimeout(5000);
            httpURLConnection.setDoInput(true);
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setUseCaches(true);

            if (httpURLConnection.getResponseCode() == 200) {
                InputStream inputStream = httpURLConnection.getInputStream();
                FileOutputStream fileOutputStream = new FileOutputStream("./res/tomcat.jpg");
                System.out.println("Request succeed!");
                saveImage(fileOutputStream, inputStream);
                System.out.println("Save Image succeed!");
            } else {
                System.out.println("Request failed!");
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void saveImage(FileOutputStream fileOutputStream, InputStream inputStream) {
        int length;
        byte buffer[] = new byte[1024];
        while (true) {
            try {
                if ((length = inputStream.read(buffer)) == -1) {
                    break;
                }
                fileOutputStream.write(buffer, 0, length);
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
    }

    public static void main(String[] args) {
        Tomcat tomcat = new Tomcat();
        tomcat.getImage("tomcat.png");
    }
}


测试结果
路径./res/tomcat.png


最后

由于博主水平有限，不免有疏漏之处，欢迎读者随时批评指正，以免造成不必要的误解！

搭建tomcat图片服务器只需两步：
（1）修改tomcat端口
（2）配置路径
找到conf文件夹下的server.xml，按需修改配置文件，然后启动tomcat服务器即可。
修改后的server.xml文件如下：
<?xml version='1.0' encoding='utf-8'?>
<!--
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
-->
<!-- Note:  A "Server" is not itself a "Container", so you may not
     define subcomponents such as "Valves" at this level.
     Documentation at /docs/config/server.html
 -->
<!-- 8005修改为8006 -->
<Server port="8006" shutdown="SHUTDOWN">
  <Listener className="org.apache.catalina.startup.VersionLoggerListener" />
  <!-- Security listener. Documentation at /docs/config/listeners.html
  <Listener className="org.apache.catalina.security.SecurityListener" />
  -->
  <!--APR library loader. Documentation at /docs/apr.html -->
  <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" />
  <!--Initialize Jasper prior to webapps are loaded. Documentation at /docs/jasper-howto.html -->
  <Listener className="org.apache.catalina.core.JasperListener" />
  <!-- Prevent memory leaks due to use of particular java/javax APIs-->
  <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" />
  <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" />
  <Listener className="org.apache.catalina.core.ThreadLocalLeakPreventionListener" />

  <!-- Global JNDI resources
       Documentation at /docs/jndi-resources-howto.html
  -->
  <GlobalNamingResources>
    <!-- Editable user database that can also be used by
         UserDatabaseRealm to authenticate users
    -->
    <Resource name="UserDatabase" auth="Container"
              type="org.apache.catalina.UserDatabase"
              description="User database that can be updated and saved"
              factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
              pathname="conf/tomcat-users.xml" />
  </GlobalNamingResources>

  <!-- A "Service" is a collection of one or more "Connectors" that share
       a single "Container" Note:  A "Service" is not itself a "Container",
       so you may not define subcomponents such as "Valves" at this level.
       Documentation at /docs/config/service.html
   -->
  <Service name="Catalina">

    <!--The connectors can use a shared executor, you can define one or more named thread pools-->
    <!--
    <Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
        maxThreads="150" minSpareThreads="4"/>
    -->


    <!-- A "Connector" represents an endpoint by which requests are received
         and responses are returned. Documentation at :
         Java HTTP Connector: /docs/config/http.html (blocking & non-blocking)
         Java AJP  Connector: /docs/config/ajp.html
         APR (HTTP/AJP) Connector: /docs/apr.html
         Define a non-SSL HTTP/1.1 Connector on port 8080
    -->
	<!-- 8080修改为8081,8443修改为8444 -->
    <Connector port="8081" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8444" />
    <!-- A "Connector" using the shared thread pool-->
    <!--
    <Connector executor="tomcatThreadPool"
               port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />
    -->
    <!-- Define a SSL HTTP/1.1 Connector on port 8443
         This connector uses the BIO implementation that requires the JSSE
         style configuration. When using the APR/native implementation, the
         OpenSSL style configuration is required as described in the APR/native
         documentation -->
    <!--
    <Connector port="8443" protocol="org.apache.coyote.http11.Http11Protocol"
               maxThreads="150" SSLEnabled="true" scheme="https" secure="true"
               clientAuth="false" sslProtocol="TLS" />
    -->

    <!-- Define an AJP 1.3 Connector on port 8009 -->
	<!-- 8009修改为8010,8443修改为8444 -->
    <Connector port="8010" protocol="AJP/1.3" redirectPort="8444" />


    <!-- An Engine represents the entry point (within Catalina) that processes
         every request.  The Engine implementation for Tomcat stand alone
         analyzes the HTTP headers included with the request, and passes them
         on to the appropriate Host (virtual host).
         Documentation at /docs/config/engine.html -->

    <!-- You should set jvmRoute to support load-balancing via AJP ie :
    <Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1">
    -->
    <Engine name="Catalina" defaultHost="localhost">

      <!--For clustering, please take a look at documentation at:
          /docs/cluster-howto.html  (simple how to)
          /docs/config/cluster.html (reference documentation) -->
      <!--
      <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>
      -->

      <!-- Use the LockOutRealm to prevent attempts to guess user passwords
           via a brute-force attack -->
      <Realm className="org.apache.catalina.realm.LockOutRealm">
        <!-- This Realm uses the UserDatabase configured in the global JNDI
             resources under the key "UserDatabase".  Any edits
             that are performed against this UserDatabase are immediately
             available for use by the Realm.  -->
        <Realm className="org.apache.catalina.realm.UserDatabaseRealm"
               resourceName="UserDatabase"/>
      </Realm>

      <Host name="localhost"  appBase="webapps"
            unpackWARs="true" autoDeploy="true">

        <!-- SingleSignOn valve, share authentication between web applications
             Documentation at: /docs/config/valve.html -->
        <!--
        <Valve className="org.apache.catalina.authenticator.SingleSignOn" />
        -->
        
		<!-- 配置路径，docBase是图片存储的地址 -->
        <Context path="/img" docBase="/usr/local/pic" reloadable="false"></Context>
        
        <!-- Access log processes all example.
             Documentation at: /docs/config/valve.html
             Note: The pattern used is equivalent to using pattern="common" -->
        <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"
               prefix="localhost_access_log." suffix=".txt"
               pattern="%h %l %u %t "%r" %s %b" />

      </Host>
    </Engine>
  </Service>
</Server>
运行结果如下：

tomcat图片验证码报错

场景：在linux服务器上，java后端生成图片验证码。后台报错找不到类
解决方案：

1.修改catalina.sh

JAVA_OPTS增加参数-Djava.awt.headless=true

JAVA_OPTS="$JAVA_OPTS $JSSE_OPTS -Djava.awt.headless=true"

2.重新启动生效