Springboot内置的工具类之StringUtils

超、凢脫俗 2024-03-30 08:49 158阅读 0赞

在实际的业务开发中，除了经常有针对对象的判断或操作以外，经常也会遇到的就是字符串的判断和操作。比如判断字符串是否为空、是否以某个字符结尾、去除头部和尾部的空白字符、字符的查找和替换。在Spring的核心包中存在这样一个类org.springframework.util.StringUtils，它提供了常见的关于字符串的判断和操作的静态方法。下面咱们针对一些常见的一块学习一下，顺便再把前面说的断言给复习一下：

## org.springframework.util.StringUtils ##

### 字符串判断 ###

判断字符串是否为 null，或 ""。注意，包含空白符的字符串为非空。

boolean isEmpty(Object str)

@Test
    public void test() {
        String name = "";
        boolean empty = StringUtils.isEmpty(name);
        Assert.isTrue(empty, "变量name是有值的");
        System.out.println("给name赋值为zhangsan");
        name = "zhangsan";
        boolean empty1 = StringUtils.isEmpty(name);
        Assert.isTrue(empty1, "变更name是有值的");
    }

判断字符串是否是以指定内容结束。忽略大小写。

boolean endsWithIgnoreCase(String str, String suffix)

@Test
    public void test2() {
        String name = "zhangsanAK";
        boolean ak = StringUtils.endsWithIgnoreCase(name, "ak");
        Assert.isTrue(ak, "变量name不是以ak结尾的");
        boolean akb = StringUtils.endsWithIgnoreCase(name, "akb");
        Assert.isTrue(akb, "变量name不是以akb结尾的");
    }

判断字符串是否已指定内容开头。忽略大小写。

boolean startsWithIgnoreCase(String str, String prefix)

@Test
    public void test3() {
        String name = "OKzhangsan";
        boolean ok = StringUtils.startsWithIgnoreCase(name, "ok");
        Assert.isTrue(ok, "变量name不是以ak结尾的");
        boolean abc = StringUtils.startsWithIgnoreCase(name, "abc");
        Assert.isTrue(abc, "变量name不是以abc开始的");
    }

是否包含空白符。

boolean containsWhitespace(String str)

@Test
    public void test4() {
        String name = "OK zhangsan";
        boolean spaceFlag = StringUtils.containsWhitespace(name);
        Assert.isTrue(spaceFlag, "变量name没有包含空格");
        System.out.println("给name赋值为zhangsan");
        name = "zhangsan";
        boolean spaceFlag2 = StringUtils.containsWhitespace(name);
        Assert.isTrue(spaceFlag2, "变量name没有包含空格");
    }

判断字符串非空且长度不为 0，即，Not Empty。

boolean hasLength(CharSequence str)

@Test
    public void test5() {
        String name = "zhangsan";
        boolean lengthFlag = StringUtils.hasLength(name);
        Assert.isTrue(lengthFlag, "变量name非空,但是长度为0");
        System.out.println("给name赋值为一个空字符串");
        name = " ";
        boolean lengthFlag2 = StringUtils.hasLength(name);
        Assert.isTrue(lengthFlag2, "变量name非空,但是长度为0");
        System.out.println("给name赋值为一个空字符串,但长度为0");
        name = "";
        boolean lengthFlag3 = StringUtils.hasLength(name);
        Assert.isTrue(lengthFlag3, "变量name非空,但是长度为0");
    }

判断字符串是否包含实际内容，即非仅包含空白符，也就是 Not Blank。这里要特别注意一下，通常empty是指null、“”，“ ”，多个空字符就不会认为是Empty了，而是Blank；

boolean hasText(CharSequence str)

@Test
    public void test6() {
        String name = "zhangsan";
        boolean lengthFlag = StringUtils.hasText(name);
        Assert.isTrue(lengthFlag, "变量name非空,但是长度为0");
        System.out.println("给name赋值为一个空字符串");
        name = "      ";
        boolean lengthFlag2 = StringUtils.hasText(name);
        Assert.isTrue(lengthFlag2, "变量是一个空字符");
    }

判断字符串指定索引处是否包含一个子串。

boolean substringMatch(CharSequence str, int index, CharSequence substring)

@Test
    public void test7() {
        String msg = "I am zhangsan";
        boolean lengthFlag = StringUtils.substringMatch(msg, 5, "zhangsan");
        Assert.isTrue(lengthFlag, "变量msg的索引位置为5的地方,是zhangsan");
        msg = "I am not zhangsan";
        boolean lengthFlag2 = StringUtils.substringMatch(msg, 5, "zhangsan");
        Assert.isTrue(lengthFlag2, "变量msg的索引位置为5的地方,是zhangsan");
    }

计算一个字符串中指定子串的出现次数。

int countOccurrencesOf(String str, String sub)

@Test
    public void test8() {
        String msg = "aaa";
        int count = StringUtils.countOccurrencesOf(msg, "a");
        Assert.isTrue(count == 3, "变量msg中没有包含3个a");
        msg = "bbb";
        int count2 = StringUtils.countOccurrencesOf(msg, "b");
        Assert.isTrue(count2==4, "变量msg中没有包含4个b");
    }

### 字符串操作 ###

查找并替换指定子串。

String replace(String inString, String oldPattern, String newPattern)

@Test
    public void test10() {
        String name = "aba";
        String name2 = StringUtils.replace(name, "b", "a");
        Assert.isTrue(name2.equals("aaa"), "变量name替换b后结果不是aaa");
    }

去除尾部的特定字符。

String trimTrailingCharacter(String str, char trailingCharacter)

@Test
    public void test11() {
        String name = "aba";
        String a = StringUtils.trimTrailingCharacter(name, 'a');
        Assert.isTrue(a.equals("ab"), "去除尾部的a后不是ab");
    }

去除头部的特定字符。

String trimLeadingCharacter(String str, char leadingCharacter)

@Test
    public void test12() {
        String name = "aba";
        String a = StringUtils.trimLeadingCharacter(name, 'a');
        Assert.isTrue(a.equals("ba"), "去除开头的a后不是ba");
    }

去除头部的空白符。

String trimLeadingWhitespace(String str)

@Test
    public void test13() {
        String name = "aba  ";
        String a = StringUtils.trimTrailingWhitespace(name);
        Assert.isTrue(a.equals("aba"), "去除尾部的空格失败了");
    }

去除头部的空白符。

String trimTrailingWhitespace(String str)

@Test
    public void test14() {
        String name = "   aba";
        String a = StringUtils.trimLeadingWhitespace(name);
        Assert.isTrue(a.equals("aba"), "去除开头的空格失败了");
    }

去除头部和尾部的空白符。

String trimWhitespace(String str)

@Test
    public void test15() {
        String name = "   aba    ";
        String a = StringUtils.trimWhitespace(name);
        Assert.isTrue(a.equals("aba"), "去除开头和尾部的空格失败了");
    }

删除开头、结尾和中间的空白符。

String trimAllWhitespace(String str)

@Test
    public void test16() {
        String name = "   a   b   a    ";
        String a = StringUtils.trimAllWhitespace(name);
        Assert.isTrue(a.equals("aba"), "去除开头、中间、尾部的空格失败了");
    }

删除指定子串。

String delete(String inString, String pattern)

@Test
    public void test17() {
        String name = "abcabc";
        String a = StringUtils.delete(name,"bc");
        Assert.isTrue(a.equals("aa"), "删除变更name里的字符b失败了");
    }

对数组的每一项执行 trim() 方法。

String\[\] trimArrayElements(String\[\] array)

@Test
    public void test18() {
        String[] names = {" zhangsan " ," li si "};
        String[] arr = StringUtils.trimArrayElements(names);
        for (String s : arr) {
            Assert.isTrue(s.equals("zhangsan")||s.equals("lisi"), "字符"+s+"中没有包含zhangsan或lisi");
        }
    }

将 URL 字符串进行解码。

String uriDecode(String source, Charset charset)

@Test
    public void test19() {
        String result="http://localhost:8080/abc?name=zhangsan";
        String url="http%3A%2F%2Flocalhost%3A8080%2Fabc%3Fname%3Dzhangsan";
        String tmp = StringUtils.uriDecode(url, Charset.forName("utf-8"));
        Assert.isTrue(result.equals(tmp), "解码失败");
    }

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> 
> [Springboot扩展点之ApplicationContextInitializer][Springboot_ApplicationContextInitializer]
> 
> [Springboot扩展点之BeanDefinitionRegistryPostProcessor][Springboot_BeanDefinitionRegistryPostProcessor]
> 
> [Springboot扩展点之BeanFactoryPostProcessor][Springboot_BeanFactoryPostProcessor]
> 
> [Springboot扩展点之BeanPostProcessor][Springboot_BeanPostProcessor]
> 
> [Springboot扩展点之InstantiationAwareBeanPostProcessor][Springboot_InstantiationAwareBeanPostProcessor]
> 
> [Springboot扩展点之SmartInstantiationAwareBeanPostProcessor][Springboot_SmartInstantiationAwareBeanPostProcessor]
> 
> [Springboot扩展点之ApplicationContextAwareProcessor][Springboot_ApplicationContextAwareProcessor]
> 
> [Springboot扩展点之@PostConstruct][Springboot_PostConstruct]
> 
> [Springboot扩展点之InitializingBean][Springboot_InitializingBean]
> 
> [Springboot扩展点之DisposableBean][Springboot_DisposableBean]
> 
> [Springboot扩展点之SmartInitializingSingleton][Springboot_SmartInitializingSingleton]
> 
> Springboot核心功能工作原理：
> 
> [Springboot实现调度任务的工作原理][Springboot]
> 
> [Springboot事件监听机制的工作原理][Springboot 1]

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[Springboot_ApplicationContextInitializer]: https://blog.csdn.net/fox9916/article/details/128522598
[Springboot_BeanDefinitionRegistryPostProcessor]: https://blog.csdn.net/fox9916/article/details/128538625
[Springboot_BeanFactoryPostProcessor]: https://blog.csdn.net/fox9916/article/details/128823328
[Springboot_BeanPostProcessor]: https://blog.csdn.net/fox9916/article/details/128917992
[Springboot_InstantiationAwareBeanPostProcessor]: https://blog.csdn.net/fox9916/article/details/128941464
[Springboot_SmartInstantiationAwareBeanPostProcessor]: https://blog.csdn.net/fox9916/article/details/128976944
[Springboot_ApplicationContextAwareProcessor]: https://blog.csdn.net/fox9916/article/details/128990305
[Springboot_PostConstruct]: https://blog.csdn.net/fox9916/article/details/128998846
[Springboot_InitializingBean]: https://blog.csdn.net/fox9916/article/details/129016083
[Springboot_DisposableBean]: https://blog.csdn.net/fox9916/article/details/129026156?spm=1001.2014.3001.5501
[Springboot_SmartInitializingSingleton]: https://blog.csdn.net/fox9916/article/details/129042652
[Springboot]: https://blog.csdn.net/fox9916/article/details/128483069
[Springboot 1]: https://blog.csdn.net/fox9916/article/details/128225155