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README
Apache-2.0

mzlion-core

============

Maven CentralLicense

Java常用的工具集合

简介

该项目是一个Java基础工具类,目前提供了对文件、流、字符串、日期、JSON和集合等JDK方法进行封装,是我平时写项目的积累和总结。项目也参考了Apache Commons Lang和JODD里的一些写法,不过大部分还是自己写的。并且提供了详细的注释。

依赖说明

本项目依赖了2个基础jar

  1. slf4j-api 为了记录日志
  2. gson JSON字符串和JavaBean相互转换的默认框架

使用

maven

<dependency>
    <groupId>com.mzlion</groupId>
    <artifactId>mzlion-core</artifactId>
    <version>1.0.10-Final</version>
</dependency>

gradle com.mzlion:mzlion-core:1.1.10-Final

文档

StringUtils工具类

我像这个StringUtils这个工具类的使用频率应该是最大的,毕竟我们平时开发项目的时候处理字符串比例大。

  1. 非常常见的方法:isEmpty(),hasLength(),hasText() isEmpty()hasLength()返回值正好相反,所以这里介绍下hasLength()判断逻辑,首先校验字符串是否为空,其次判断字符串的长度是否大于0。hasText()除了hasLength()校验逻辑之外,还判断了字符串是否至少存在一个非空白字符,所谓空白字符有空格、制表符等。
  2. trim()方法 该方法主要用来去除字符串两边的空白字符,相比系统的String.trim()提供的方法,该方法不会出现NullPointException,并且不采用正则剔除,速度略微稍好。
  3. replace()方法 该方法比系统String.replace()方法执行效率更高,因为该方法不支持正则匹配,如果必须要正则处理,请使用系统提供的替换方法。
  4. split()方法 该方法同样比系统String.split()方法执行效率更高,因为该方法不支持正则匹配,如果必须要正则处理,请使用系统提供的替换方法。
  5. toUnderline()方法 该方法将驼峰式命名的字符串转为下划线字符串,比如字符串HelloWorld会转为hello_world
  6. isDigital()方法 该方法用于判断是否是纯数字组成。
  7. isNumeric() 该方法判断是否是数值类型的字符串。

CollectionUtils工具类

这个类专门操作Map及其子类、Collection及其子类的集合工具类。在实际开发中应用的也比较多。

  1. 非常常见的方法:isEmpty(),isNotEmpty() 主要判断集合是否为空或非空
  2. toString(Map<String, String>)方法 该方法将Map数据转为字符串,默认采用URL参数拼接格式风格。形如如下实例
        Map<String,String> params = new HashMap<>();
        params.put("username","admin");
        params.put("password","123456");
        String str = CollectionUtils.toString(params);
        //则得到的字符串结果为 "username=admin&password=123456"
  3. asCommonSignString(Map<String, String> params) 在做接口通讯时经常需要签名验签,目前通用规则是:将参数按照字母自然排序, 参数之间使用&连接符组成一个待签名的字符串,形如charset=UTF-8&ordAmt=1&ordDetail=Iphone十台&signType=1.那个这个方法就是干这件事情的。

gson.JsonUtil工具类

gson.JsonUtil是对Gson的封装,与其同类名的还有fastjson.JsonUtil. 本项目默认使用的Gson,如果需要需要fastjson.JsonUtil的,需要手动引入fastjon的依赖

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>${fastjson.version}</version>
</dependency>

两个工具类的提供的方法基本类似,下面着重介绍gson.JsonUtil,以下简称JsonUtil

JsonUtil是提供了将JavaBean和JSON字符串相互转换的功能,并且该工具类自动忽略静态属性和transient属性,另外对属性值为null也是直接忽略。

  1. JsonUtil.toJson(T value) 将JavaBean对象转为JSON字符串,这个方法也是使用频率极高的。
  2. JsonUtil.toJson(T value,String[] ignorePropertyNames) 将JavaBean对象转为JSON字符串,并且根据ignorePropertyNames过滤属性
  3. JsonUtil.toJson(T value,boolean toUnicode,String[] ignorePropertyNames) 将JavaBean对象转为JSON字符串, 并且额外提供了将非ASCII码转为Unicode码,便于在网络通讯时出现乱码的解决之道;
  4. JsonUtil.toJson(T value,boolean toUnicode,boolean ignoreNull,String[] ignorePropertyNames) 将JavaBean对象转为JSON字符串, 工具默认是直接忽略值为null的属性,那么此方法提供便于调用者可以自动,这个方法也是最全最具有控制权的一个方法了。
  5. 'JsonUtil.fromJson(String json,Class clazz)' 将JSON字符串转为JavaBean对象,这个方法也是使用率比较高的。
  6. 'JsonUtil.fromJson(String json,TypeToken typeToken)' 将JSON字符串转为JavaBean对象,本方法主要针对带有泛型类型的JavaBean。 这个方法的用法下面特别举例说明下,因为TypeToken需要使用子类实例对象,这个是对能够解析出泛型描述的手段。
    String jsonArray = "[{\"userId\":\"u2016071301\",\"userName\":\"张三\"},{\"userId\":\"u2016071302\",\"userName\":\"李四\"}]";
    List<Person> personList = JsonUtil.fromJson(jsonArray,new TypeToken<List<Person>>(){
    });
    //主要TypeToken使用的子类对象

ArrayUtils工具类

这个类专门操作数组的工具类,提供了空、非空判断,强大的toString()方法,toString()方法提供非常多的重载方法,调用方式也非常简单。

NumberUtils工具类

这是一个数值的工具类,目前仅仅提供了数字、实数的判断,科学计数法的转为可展示的普通字符串。

新增加了金额元和分的相互转化,解决了形如10.445这种临界值四舍五入时未得到期望值10.45

PlaceholderPropertyResolver类

这是一个针对.properties格式的处理类,该类特点主要有:

  • 支持classpath:文件路径写法
  • 支持多配置文件读取,重名的key会被覆盖
  • 支持${key}语法,其中key可以是当前文件的属性名,也可以系统的属性名
  • 支持Builder模式,不过这个目前好处体现不大

用法也非常简单,下面举例说明

    PropertyResolver propertyResolver = new PlaceholderPropertyResolver.Builder()
        .path("classpath:system.properties")
        .build();
    String port = propertyResolver.getProperty("port");
    Assert.assertEquals("3306", port);

下面再来介绍这个类的一些常用方法

  1. containsProperty(String key) 判断key是存在
  2. 'getAllProperties()' 返回所有的键值对
  3. getProperty(String key) 返回key的值
  4. getProperty(String key, String defaultValue) 返回key的值,如果值为null则默认值defaultValue
  5. getProperty(String key, Class<T> targetType) 返回key的值,并且根据返回值类型尝试自动转换

IOUtils工具类

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常用工具类 展开 收起
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