Maven作用
Maven主要作用是使用它来导入第三方jar包
管理项目
下载Maven
下载地址：http://maven.apache.org/download.cgi
image-20200718084505519
修改配置
打开./apache-maven-3.6.3/conf/settings.xml
修改mirrors
<mirrors>
<mirror>
<id>nexus-aliyunid>
<mirrorOf>*mirrorOf>
<name>Nexus aliyunname>
<url>https://maven.aliyun.com/repository/centralurl>
mirror>
mirrors>
修改本地存储路径localRepository
<localRepository>/Users/zhongxin/maven_downloadlocalRepository>
设置环境变量
将解压后的文件夹移动到/usr/local/apache-maven-3.6.3
$ vi ~/.bash_profile
进入文件后添加下面两行
export MAVEN_HOME=/usr/local/apache-maven-3.6.3
export PATH=$PATH:$MAVEN_HOME/bin
添加后保存
$ source ~/.bash_profile
测试
测试
IDEA中配置
IDEA中配置
新建Maven项目
选择新建Maven项目
1
选择存放路径
2
查看项目结构
项目结构
新建存放非代码的文件夹resources
新建文件夹
添加第三方包的方法
第三方包仓库https://mvnrepository.com/
以解析json的第三方库fastjson为例
进入mvnrepository搜索想要使用的第三方包
找到需要使用的版本
拷贝xml内容
<dependency>
<groupId>com.alibabagroupId>
<artifactId>fastjsonartifactId>
<version>1.2.72version>
dependency>
第三方包
<?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>4.0.0modelVersion>
<groupId>org.examplegroupId>
<artifactId>learn_java_mavenartifactId>
<version>1.0-SNAPSHOTversion>
<dependencies>
<dependency>
<groupId>com.alibabagroupId>
<artifactId>fastjsonartifactId>
<version>1.2.72version>
dependency>
dependencies>
project>
fastjson
fastjson工具类，静态方法
静态方法不需要创建对象，直接用 类名点 调用
导入
import com.alibaba.fastjson.JSONObject;
json字符串转成java对象
待转化json
{"name": "张三","age": 18,"source": 100}
定义一个Student类来接收
package com.zhongxin.json;
public class Student {
private String name;
private int age;
private int score;
public Student(String name, int age, int score) {
this.name = name;
this.age = age;
this.score = score;
}
public Student() {
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
", score=" + score +
'}';
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}
}
转化主函数
package com.zhongxin.json;
import com.alibaba.fastjson.JSONObject;
public class Json {
public static void main(String[] args) {
String json = "{\"name\": \"张三\",\"age\": 18,\"source\": 100}";
Student s = JSONObject.parseObject(json, Student.class);
System.out.println(s);
}
}
输出：Student{name='张三', age=18, score=0}
运行提示
警告提示
在pom.xml中添加如下内容：
<properties>
<maven.compiler.target>1.8maven.compiler.target>
<maven.compiler.source>1.8maven.compiler.source>
<project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8project.reporting.outputEncoding>
<maven.compiler.encoding>UTF-8maven.compiler.encoding>
<aspectj.version>1.9.2aspectj.version>
properties>
不再提示警告
java对象转化为json字符串
Student s2 = new Student("李四", 20, 90);
String json2 = JSONObject.toJSONString(s2);
System.out.println(json2);
输出{"age":20,"name":"李四","score":90}
json字符串转Map
Map map = JSONObject.parseObject(json, Map.class);
System.out.println(map);
输出{name=张三, source=100, age=18}
map转json字符串
String json3 = JSONObject.toJSONString(map);
System.out.println(json3);
输出{"name":"张三","source":100,"age":18}
json数组字符串转java对象
待转化：[{"name": "张三","age": 18},{"name": "李四","age": 16}]
定义Teacher类
package com.zhongxin.json;
public class Teacher {
private String name;
private int age;
public Teacher() {
}
public Teacher(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
@Override
public String toString() {
return "Teacher{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
public void setAge(int age) {
this.age = age;
}
public void setName(String name) {
this.name = name;
}
}
转化
package com.zhongxin.json;
import com.alibaba.fastjson.JSONObject;
import java.util.List;
public class Json2 {
public static void main(String[] args) {
String json = "[{\"name\": \"张三\",\"age\": 18},{\"name\": \"李四\",\"age\": 16}]";
List list = JSONObject.parseArray(json, Teacher.class);for (Teacher t : list) {
System.out.println(t);
}
}
}
输出内容：
Teacher{name='张三', age=18}
Teacher{name='李四', age=16}
Properties
使用Properties一般不使用Map接口的方法
Properties没有泛型，默认String
先要修改文件编码
修改编码
新建一个config.properties文件../learn_java_maven/src/test/resources/config.properties
写入配置文件
package com.zhongxin.properties;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;
public class PropDemo {
public static void main(String[] args) throws IOException {
Properties prop = new Properties();
prop.setProperty("USERNAME", "张三");
prop.setProperty("PASSWORD", "123456");
System.out.println(prop.getProperty("USERNAME"));
System.out.println(prop.getProperty("PASSWORD"));
FileOutputStream fos = new FileOutputStream("src/test/resources/config.properties");
prop.save(fos, "注释");
fos.close();
}
}
查看config.properties文件
#注释
#Sat Jul 18 10:05:03 CST 2020
USERNAME=张三
PASSWORD=123456
读取配置文件
FileInputStream fis = new FileInputStream("src/test/resources/config.properties");
prop.load(fis);
System.out.println(prop);
输出：{USERNAME=张三, PASSWORD=123456}
异常捕获
throws
try
throws
往外抛出异常
try
可以进行异常捕获
try{
// 可能异常的代码
}catch(Exception e){
// 捕获异常，出现异常的解决方案
}finally{
// 释放资源
// 无论是否异常，一定会执行的代码
}
转播
