Java on Coding

优雅的关闭springboot程序

Sat, 26 Oct 2019 00:00:00 +0000

使用jar形式部署springboot程序后，通过kill进程关闭程序，总是不踏实。好在，官方提供了优雅关闭应用程序的方式。

引入依赖

首先，在POM中引入依赖

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

配置application

以2.1.8.RELEASE为例，application.yml配置如下：

management:
  endpoint:
    shutdown:
      enabled: true
  endpoints:
    web:
      exposure:
        include: "*"
      base-path: /actuator

发送POST请求

curl -d "" --header "Content-Type:application/json" http://127.0.0.1:8080/actuator/shutdown
{"message":"Shutting down, bye..."}

Spring Boot Actuator

actuator可以帮助你监控和管理Spring Boot应用，比如健康检查、审计、统计和HTTP追踪等。所有的这些特性可以通过JMX或者HTTP endpoints来获得。
Actuator通过创建Endpoint来暴露HTTP或者JMX来监控和管理应用。

mybatis sql中使用<或<=时报错SAXParseException

Thu, 10 Oct 2019 00:00:00 +0000

使用mybatis时，当sql中使用<或<=时：

SELECT * FROM user WHERE age < 36
SELECT * FROM user WHERE age <= 36

会报错SAXParseException: 元素内容必须由格式正确的字符数据或标记组成。

org.apache.ibatis.builder.BuilderException: Error creating document instance.  Cause: org.xml.sax.SAXParseException; lineNumber: 7; columnNumber: 37; 元素内容必须由格式正确的字符数据或标记组成。
	at org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:596) ~[mybatis-spring-2.0.2.jar:2.0.2]
	at org.mybatis.spring.SqlSessionFactoryBean.afterPropertiesSet(SqlSessionFactoryBean.java:475) ~[mybatis-spring-2.0.2.jar:2.0.2]
	at org.mybatis.spring.SqlSessionFactoryBean.getObject(SqlSessionFactoryBean.java:616) ~[mybatis-spring-2.0.2.jar:2.0.2]
	at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration.sqlSessionFactory(MybatisAutoConfiguration.java:180) ~[mybatis-spring-boot-autoconfigure-2.1.0.jar:2.1.0]
	at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$9adef889.CGLIB$sqlSessionFactory$1(<generated>) ~[mybatis-spring-boot-autoconfigure-2.1.0.jar:2.1.0]
	at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$9adef889$$FastClassBySpringCGLIB$$abadc28a.invoke(<generated>) ~[mybatis-spring-boot-autoconfigure-2.1.0.jar:2.1.0]
	at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244) ~[spring-core-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:363) ~[spring-context-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$9adef889.sqlSessionFactory(<generated>) ~[mybatis-spring-boot-autoconfigure-2.1.0.jar:2.1.0]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_172]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_172]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_172]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_172]
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE]
	... 44 common frames omitted
Caused by: org.apache.ibatis.builder.BuilderException: Error creating document instance.  Cause: org.xml.sax.SAXParseException; lineNumber: 7; columnNumber: 37; 元素内容必须由格式正确的字符数据或标记组成。
	at org.apache.ibatis.parsing.XPathParser.createDocument(XPathParser.java:260) ~[mybatis-3.5.2.jar:3.5.2]
	at org.apache.ibatis.parsing.XPathParser.<init>(XPathParser.java:126) ~[mybatis-3.5.2.jar:3.5.2]
	at org.apache.ibatis.builder.xml.XMLMapperBuilder.<init>(XMLMapperBuilder.java:80) ~[mybatis-3.5.2.jar:3.5.2]
	at org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:593) ~[mybatis-spring-2.0.2.jar:2.0.2]
	... 57 common frames omitted
Caused by: org.xml.sax.SAXParseException: 元素内容必须由格式正确的字符数据或标记组成。
	at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:203) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:177) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:400) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:327) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1472) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.startOfMarkup(XMLDocumentFragmentScannerImpl.java:2635) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2732) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:602) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:505) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:842) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:771) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:243) ~[na:1.8.0_172]
	at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:339) ~[na:1.8.0_172]
	at org.apache.ibatis.parsing.XPathParser.createDocument(XPathParser.java:258) ~[mybatis-3.5.2.jar:3.5.2]
	... 60 common frames omitted

这是由于mybatis的SQL配置在XML中，一些特殊符号在XML解析时被转义。

maven加载本地jar包

Sun, 29 Sep 2019 00:00:00 +0000

添加引用，开发已经没有问题。

<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-jdk15on</artifactId>
    <version>152</version>
    <scope>system</scope>
    <systemPath>${project.basedir}/src/main/resources/lib/xxxx.jar</systemPath>
</dependency>

打包如果是springboot项目，只需要配上includeSystemScope即可：

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

springboot整合mybatis

Wed, 25 Sep 2019 00:00:00 +0000

添加Maven依赖

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>RELEASE</version>
</dependency>

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>RELEASE</version>
</dependency>

在application.yml中配置数据源和mybatis

server:
  port: 8080

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    url: jdbc:mysql://127.0.0.1:3306/test1?jdbcCompliantTruncation=false&allowMultiQueries=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: root

mybatis:
  mapper-locations: classpath:mapper/*.xml

mysql

CREATE TABLE `user` (
	`id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT,
	`name` VARCHAR(50) NULL DEFAULT NULL,
	`age` INT(11) UNSIGNED NULL DEFAULT NULL,
	PRIMARY KEY (`id`)
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB
AUTO_INCREMENT=3;

INSERT INTO `user` (`id`, `name`, `age`) VALUES (1, 'alita', 23);
INSERT INTO `user` (`id`, `name`, `age`) VALUES (2, 'sofia', 33);

DAO

├─main
│  ├─java
│  │  └─top
│  │      └─guoj
│  │          └─springboot
│  │              ├─controller
│  │              ├─dao
│  │              ├─entity
│  │              └─service
│  └─resources
│      └─mapper

UserDao.java

package top.guoj.springboot.dao;

import org.apache.ibatis.annotations.Mapper;

import java.util.List;
import java.util.Map;

@Mapper
public interface UserDao {
	List<Map<String, Object>> getUser();
}

UserDao.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="top.guoj.springboot.dao.UserDao">

    <select id="getUser" resultType="java.util.HashMap">
      select * from user;
    </select>

</mapper>

使用

package top.guoj.springboot.controller;

import com.alibaba.fastjson.JSONObject;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import top.guoj.springboot.dao.UserDao;

import java.util.List;
import java.util.Map;

@RestController
public class HelloController {

	@Autowired
	private UserDao userDao;

	@RequestMapping("/mybatis")
	String mybatis() {
		List<Map<String, Object>> users = userDao.getUser();
		return JSONObject.toJSONString(users);
	}
}

在配置application.yml文件中使用自定义属性

Wed, 25 Sep 2019 00:00:00 +0000

引入springboot依赖

pom.xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-configuration-processor</artifactId>
    <optional>true</optional>
</dependency>

自定义属性

在application.properties中配置自定义属性。

top.guoj.user-name=hello
top.guoj.pass-word=word

## OR
top.guoj.userName=hello
top.guoj.passWord=word

新建映射类

通过@ConfigurationProperties注解并配置prefix属性。

@Component
@ConfigurationProperties(prefix = "top.guoj")
public class Configure {

	private String userName;
	private String passWord;

	public String getUserName() {
		return userName;
	}

	public void setUserName(String userName) {
		this.userName = userName;
	}

	public String getPassWord() {
		return passWord;
	}

	public void setPassWord(String passWord) {
		this.passWord = passWord;
	}
}

使用

@RestController
public class HelloController {

	@Autowired
	private Configure configure;

	@RequestMapping("/configure")
	String configure() {
		return configure.getUserName() + configure.getPassWord();
	}
}

eclipse中搭建springboot helloword

Fri, 06 Jul 2018 00:00:00 +0000

安装sts(Spring Tools)

新建Spring Starter Project

项目结构如下：

application.yml

server:
  port: 8080</pre>

pom.xml

<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>2.0.2.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>

新建HelloController.java

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

@RestController
public class HelloController {

	@RequestMapping(value = "/hello", method = RequestMethod.GET)
	public String HelloController() {
		return "Hello World!";
	}

}

运行Run As->Spring Boot App

一道题说明java初始化顺序

Tue, 05 Dec 2017 06:48:48 +0000

之前，在公司内部给大家做了java培训后，要考一考大家，关于初始化方面，想了一个综合涵盖继承、静态等各个方面的代码。

题目

说出下面程序运行结果：

class Language {

	static {
		System.out.println("language static block");
	}

	{
		System.out.println("language block");
	}

	public Language() {
		System.out.println("language constructor");
	}

	public Language(String name) {
		System.out.println(name);
	}

}

public class Python extends Language {

	private String name;

	public Python(String name) {
		this.name = name;
		System.out.println("python constructor");
		System.out.println(this.name);
	}

	{
		System.out.println("python block");
	}

	static {
		System.out.println("python static block");
	}

	public static void main(String[] args) {
		new Python("hello python");
	}

答案

language static block
python static block
language block
language constructor
python block
python constructor
hello python