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javax.imageio.ImageIO.write报空指针异常,发现是没有路径directory导致

1.加入路径存在判断即可

        File directory = new File(bashPath + pinyin);
        if(!directory.exists()){
            directory.mkdir();
        }

2.完整报错:

java.lang.NullPointerException: null
    at javax.imageio.ImageIO.write(ImageIO.java:1538) ~[na:1.8.0_212]
    at com.tddlmj.rstar.controller.SpiderController.saveImage(SpiderController.java:143) ~[classes/:na]
    at com.tddlmj.rstar.controller.SpiderController.saveImg(SpiderController.java:109) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_212]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_212]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_212]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_212]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:189) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200) ~[tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1415) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_212]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_212]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.17.jar:9.0.17]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_212]

h2内置的tool可以备份还原h2数据库。

1.首先引入了h2的依赖,注意scope是compile,spring boot 默认是runtime,没法使用

  <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>compile</scope>
        </dependency>

2.要使用文件数据库,内存数据库貌似不行,

spring.datasource.url=jdbc:h2:file:~/db/mydb
spring.datasource.username=sa
spring.datasource.password=
spring.datasource.driver-class-name=org.h2.Driver
spring.jpa.hibernate.ddl-auto=update

3.java 代码

import org.h2.tools.Backup;
import org.h2.tools.Restore;
@RequestMapping("/bak")
    public String bak() throws Exception {
        String file = "~/db/bak/backup-" + JodaDateUtil.formatDate(JodaDateUtil.set000000(new Date()), "yyyy-MM-dd") + ".zip";

        Backup.execute(file, "~/db", "mydb", true);
        return "0k";
    }

    @RequestMapping("/res")
    public String res() throws Exception {
        String file = "~/db/bak/backup-" + JodaDateUtil.formatDate(JodaDateUtil.set000000(new Date()), "yyyy-MM-dd") + ".zip";
        File f = new File(file);
        int i = 1;
        while (!f.exists()) {
            DateTime d = new DateTime();
            d.minusDays(i);
            file = "~/db/bak/backup-" + JodaDateUtil.formatDate(JodaDateUtil.set000000(d.toDate()), "yyyy-MM-dd") + ".zip";
            f = new File(file);
            i++;
        }
        Restore.execute(file, "~/db", "mydb");
        return "0k";
    }

debian 9 安装nodejs 不能通过apt-get直接装,一下是安装方法

1.安装

sudo apt-get update
curl -sL https://deb.nodesource.com/setup_8.x | sudo -E bash -
sudo apt-get install build-essential nodejs
  1. 测试
node -v
npm -v

这个是linux机器,建议使用kvm来虚拟运行安卓app.
我的是archlinux

首先最首要的一点,bios中开启intel Virtualization Technology ----enable。。

如果这个开启后不行了,再做下面的操作

1.检查是否支持虚拟化,0表示不支持

$:LC_ALL=C lscpu | grep Virtualization
Virtualization:      VT-x

2.是否核心支持kvm

$ zgrep CONFIG_KVM /proc/config.gz
CONFIG_KVM_GUEST=y
# CONFIG_KVM_DEBUG_FS is not set
CONFIG_KVM_MMIO=y
CONFIG_KVM_ASYNC_PF=y
CONFIG_KVM_VFIO=y
CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT=y
CONFIG_KVM_COMPAT=y
CONFIG_KVM=m
CONFIG_KVM_INTEL=m
CONFIG_KVM_AMD=m
CONFIG_KVM_AMD_SEV=y
CONFIG_KVM_MMU_AUDIT=y

3.安装kvm

#加载内核虚拟化模块
 sudo modprobe virtio
#kvm 
sudo pacman -S  qemu  libvirt 
#如果需要图形及面
sudo pacman -S virt-manager
#连接网络需要的包
sudo pacman -S ebtables dnsmasq bridge-utils openbsd-netcat
# 当前用户加入组kvm
$ sudo usermod -a -G kvm shenfeng

手贱升级了gradle,导致sync报错---android studio 报错:Unable to find method 'org.gradle.api.tasks.TaskInputs.file,这个是因为升级了gradle导致方法不兼容。

1.下载4.10版本的gradle--- https://gradle.org/releases/
2.File---settings ---build execution,deployment---gradle 配置成你刚下载的gradle
3.build.gradle 配置,貌似升级的时候,会自动设升级这个

 dependencies {
        classpath 'com.android.tools.build:gradle:3.1.3'
}

4.如果海报错::Minimum supported Gradle version is 2.14.1,File----project structure---该下gradle版本配置。