org.apache.commons.lang.StringUtils类提供了String的常用操作,最为常用的判空有如下两种isEmpty(String str)和isBlank(String str)。
StringUtils.isEmpty(String str) 判断某字符串是否为空，为空的标准是 str==null 或 str.length()==0
System.out.println(StringUtils.isEmpty(null)); //true
System.out.println(StringUtils.isEmpty("")); //true
System.out.println(StringUtils.isEmpty(" ")); //false
System.out.println(StringUtils.isEmpty("dd")); //false
StringUtils.isNotEmpty(String str) 等价于 !isEmpty(String str)
StringUtils.isBlank(String str) 判断某字符串是否为空或长度为0或由空白符(whitespace) 构成
System.out.println(StringUtils.isBlank(null)); //true
System.out.println(StringUtils.isBlank("")); //true
System.out.println(StringUtils.isBlank(" ")); //true
System.out.println(StringUtils.isBlank("dd")); //false
StringUtils.isBlank(String str) 等价于 !isBlank(String str)
实例展示
自定义判断方法,实现同样的判断逻辑
/**
* 判断对象是否为null,不允许空白串
*
* @param object 目标对象类型
* @return
*/
public static boolean isNull(Object object){
if (null == object) {
return true;
}
if ((object instanceof String)){
return "".equals(((String)object).trim());
}
return false;
} /**
* 判断对象是否不为null
*
* @param object
* @return
*/
public static boolean isNotNull(Object object){
return !isNull(object);
}
System.out.println(StringHandler.isNull(null)); //true
System.out.println(StringHandler.isNull("")); //true
System.out.println(StringHandler.isNull(" ")); //true
System.out.println(StringHandler.isNull("dd")); //false
通常我们通过HttpServletRequest获取到的参数,需要经过判空处理,转型然后得到我们想要的值,这里可以进行这些操作的简单封装.如下
/**
* 从<code>HttpServletRequest</code>中获取<code>String</code>类型的值, 不允许传递空串
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @return
* 返回需要的值
*/
public static final String getString(HttpServletRequest request,String paramName){
return getString(request, paramName, false);
}
/**
* 从<code>HttpServletRequest</code>中获取<code>String</code>类型的值
*
* 如果传递过来的参数为包含空白字符串的字符,认为为有效值, 否则返回null
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @return
* 返回需要的值
*/
public static final String getString(HttpServletRequest request,String paramName,boolean isWithSpace) {
String tmp = request.getParameter(paramName);
if(isWithSpace){
//如果允许包含空格,则使用isEmpty判空
if (!StringUtils.isEmpty(tmp)){
return tmp;
}
}else{
if(!StringUtils.isBlank(tmp)){
return tmp;
}
}
return null;
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Long</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @return
* 返回需要的值
*/
public static final Long getLong(HttpServletRequest request,String paramName) {
return getLong(request, paramName, -1L);
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Long</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @param defaultValue
* 默认值
* @return
* 返回需要的值
*/
public static final Long getLong(HttpServletRequest request,String paramName,Long defaultValue) {
String tmp = request.getParameter(paramName);
if (!StringUtils.isBlank(tmp)){
try {
Long value = Long.parseLong(tmp);
return value;
} catch (NumberFormatException e) {
return -1L;
}
}
return defaultValue;
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Integer</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @return
* 返回需要的值
*/
public static final Integer getInt(HttpServletRequest request,String paramName) {
return getInt(request,paramName, -1);
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Integer</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @param defaultValue
* 默认值
* @return
* 返回需要的值
*/
public static final Integer getInt(HttpServletRequest request,String paramName, int defaultValue) {
String tmp = request.getParameter(paramName);
if (!StringUtils.isBlank(tmp)){
try {
Integer value = Integer.parseInt(tmp);
return value;
} catch (NumberFormatException e) {
return -1;
}
}
return defaultValue;
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Short</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @return
* 返回需要的值
*/
public static final Short getShort(HttpServletRequest request,String paramName) {
return getShort(request,paramName, (short)-1);
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Short</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @param defaultValue
* 默认值
* @return
* 返回需要的值
*/
public static final Short getShort(HttpServletRequest request,String paramName, short defaultValue) {
String tmp = request.getParameter(paramName);
if (!StringUtils.isBlank(tmp)){
try {
Short value = Short.parseShort(tmp);
return value;
} catch (NumberFormatException e) {
return (short)-1;
}
}
return defaultValue;
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Byte</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @return
* 返回需要的值
*/
public static final Byte getByte(HttpServletRequest request,String paramName) {
return getByte(request,paramName, (byte)-1);
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Byte</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @param defaultValue
* 默认值
* @return
* 返回需要的值
*/
public static final Byte getByte(HttpServletRequest request,String paramName, Byte defaultValue) {
String tmp = request.getParameter(paramName);
if (!StringUtils.isBlank(tmp)){
try {
Byte value = Byte.parseByte(tmp);
return value;
} catch (NumberFormatException e) {
return (byte)-1;
}
}
return defaultValue;
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Double</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @return
* 返回需要的值
*/
public static final Double getDouble(HttpServletRequest request,String paramName) {
return getDouble(request, paramName,-1D);
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Double</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @param defaultValue
* 默认值
* @return
* 返回需要的值
*/
public static final Double getDouble(HttpServletRequest request,String paramName, Double defaultValue) {
String tmp = request.getParameter(paramName);
if (!StringUtils.isBlank(tmp)){
try {
Double value = Double.parseDouble(tmp);
return value;
} catch (NumberFormatException e) {
return -1D;
}
}
return defaultValue;
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Float</code>类型的值
*
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @return
* 返回需要的值
*/
public static final Float getFloat(HttpServletRequest request,String paramName) {
return getFloat(request, paramName,-1F);
}
/**
* 从<code>HttpServletRequest</code>中获取<code>Float</code>类型的值
*
* @param request
* @see HttpServletRequest
* @param paramName
* 参数名称
* @param defaultValue
* 默认值
* @return
* 返回需要的值
*/
public static final Float getFloat(HttpServletRequest request,String paramName, Float defaultValue) {
String tmp = request.getParameter(paramName);
if (!StringUtils.isBlank(tmp)){
try {
Float value = Float.parseFloat(tmp);
return value;
} catch (NumberFormatException e) {
return -1F;
}
}
return defaultValue;
}
再附加个人经常用的几个String的操作
1.字符串编码转换
/**
* change UTF8 To GB2312
* @param target
* @return
*/
public static final String UTF82GB2312(String target) {
try {
return new String(target.getBytes("UTF-8"), "gb2312");
} catch (Exception localException) {
System.err.println("UTF8 TO GB2312 change error!");
}
return null;
} /**
* change UTF8 To GBK
* @param target
* @return
*/
public static final String UTF82GBK(String target) {
try {
return new String(target.getBytes("UTF-8"), "GBK");
} catch (Exception localException) {
System.err.println("UTF8 TO GBK change error!");
}
return null;
} /**
* change UTF8 To ISO8859-1
* @param target
* @return
*/
public static final String UTF82ISO(String target) {
try {
return new String(target.getBytes("UTF-8"), "ISO8859-1");
} catch (Exception localException) {
System.err.println("UTF8 TO ISO8859-1 change error!");
}
return null;
} /**
* change Windows-1252 To UTF-8
* @param target
* @return
*/
public static final String Windows1252UTF8(String target) {
try {
return new String(target.getBytes("Windows-1252"), "UTF-8");
} catch (Exception localException) {
System.err.println("Windows1252 To UTF8 chage error");
}
return null;
}
2.文本追加高亮
/**
* 给串增加颜色标签
* @param color
* @param target
* @return
*/
public static String withColor(String color, String target) {
return withColor(color, target,true);
} /**
* 给串增加颜色标签
* @param color
* @param target
* @param paramBoolean
* @return
*/
public static String withColor(String color, String target, boolean paramBoolean) {
if (paramBoolean)
return "<font color='".concat(color).concat("'>").concat(target).concat("</font>");
return target;
}
System.out.println(StringHandler.withColor("red","文本串", true));
运行结果
<font color='red'>文本串</font>