目录
前言
- 简单描述一下JexlEngine的用法，使用它可以将一段表达式转成Java代码执行。
问题描述
StringWHERE="app_id=005";
假设上面的where变量需要传递给JexlEngine调用，由于JexlEngine执行表达式的时候，一个等号（=）是会报语法错误的，需要转成两个等号（==）才能执行，如果后面还有
and、or
条件拼接，则
and
要转成
&&
，
or
要转成
||
（这一步可转可不转，不过一定不能是大写） 。
StringWHERE="pay_time > ='2019/10/21' and pay_time < = '2019/10/22' and app_id = '001'";
需求：给出上面的where条件，我们需要将有且仅有一个等号（=）的情况转成两个等号（==），>=和<=无需转换，最后再将
and
转成
&&
，
or
要转成
||
。
即想要的效果如下：
StringWHERE="pay_time > ='2019/10/21' && pay_time < = '2019/10/22' and app_id == '001'";
思路分析
我们先使用toCharArray将字符串转换为字符数组，然后根据字符的索引去判断一个等号（=）出现的位置，再进行替换成两个等号（==）。
难点：由于是根据等号（=）的索引来进行对应判断和查找，所以在进行判断的时候，需要考虑很多种格式问题，比如：
- 一个等号（=）的时候，左右有没有空格，或者是多个空格的情况，
- 如果where直接是两个等号（==）的时候，我们就忽略无需对它进行转换。
解决方案
根据上述的思路分析，我们直接上代码。
方案一
📌普通版
我们先根据需求，将大致的实现代码写出来，最后再去考虑多种情况出现的问题。
packagecom.example.business.util;importjava.util.ArrayList;/**
* @ClassName: Test
* @Description: 临时测试类
* @Author yang
* @Date 2022/12/20
* @Version 1.0
*/publicclassTest{publicstaticvoidmain(String[] args){StringWHERE="app_id='005' AND keyid='0101'";// String WHERE = "app_id=005 AND keyid=0101";// String WHERE = "app_id= 005 AND keyid = 0101";// String WHERE = "app_id=005";if(WHERE.contains("\'")){//去除字符串多余空格，只能存在一个空格（即把两个以上的空格替换成一个）ArrayList<Integer> indexList =newArrayList<>();String strChars =WHERE.replaceAll(" {2,}"," ");char[] chars = strChars.toCharArray();for(int i =0; i < chars.length; i++){if(chars[i]=='='){
indexList.add(i);}}for(Integer integer : indexList){StringBuilder builder =newStringBuilder();int index = integer;boolean appendFlag =false;if(chars[index -1]!='>'&& chars[index -1]!='<'&& chars[index -1]!='!'){if(chars[index +1]=='='){//如：String WHERE = "pay_time == '2019/10/22'";System.out.println("原句返回："+WHERE);return;}if(chars[index +1]==' '&& chars[index +2]=='='){//如：String WHERE = "pay_time = ='2019/10/22'";或String WHERE = "pay_time = = '2019/10/22'";System.out.println("22222222：");dealTwoEqual(WHERE);return;}boolean flag = chars[index +1]==' '||(chars[index +1]=='\''&& chars[index +1]!='=');//如：String WHERE = "pay_time = '2019/10/22'";或String WHERE = "pay_time = '2019/10/22'";while((index +1< chars.length)&& flag){
flag = chars[index +1]==' '||(chars[index +1]=='\''&& chars[index +1]!='=');if(flag){
appendFlag =true;
index++;}}}if(appendFlag){int arrIndex =0;for(int i =0; i < indexList.size(); i++){int value = indexList.get(i);if(value == integer){
arrIndex = i;}}if(arrIndex ==0){
builder.append(strChars,0, integer);
builder.append("==");
builder.append(strChars, index, chars.length);}else{
builder.append(strChars,0, integer +1);
builder.append("==");
builder.append(strChars, index +1, chars.length +1);}
strChars = builder.toString();}}System.out.println("builder："+ strChars);String str = strChars;if(str.contains(" and ")){
str = str.replace(" and "," && ");}if(str.contains(" AND ")){
str = str.replace(" AND "," && ");}if(str.contains(" or ")){
str = str.replace(" or "," || ");}if(str.contains(" OR ")){
str = str.replace(" OR "," || ");}System.out.println("str："+ str);}else{//去除字符串多余空格，只能存在一个空格（即把两个以上的空格替换成一个）ArrayList<Integer> indexList =newArrayList<>();String strChars =WHERE.replaceAll(" {2,}"," ");char[] chars = strChars.toCharArray();for(int i =0; i < chars.length; i++){if(chars[i]=='='){
indexList.add(i);}}for(Integer integer : indexList){StringBuilder builder =newStringBuilder();int index = integer;boolean appendFlag =false;if(chars[index -1]!='>'&& chars[index -1]!='<'&& chars[index -1]!='!'){if(chars[index +1]=='='){System.out.println("原句返回："+WHERE);return;}if(chars[index +1]==' '&& chars[index +2]=='='){System.out.println("22222222：");dealTwoEqual(WHERE);return;}boolean flag =(chars[index]=='='&& chars[index +1]==' ')||(chars[index]=='='&& chars[index +1]!=' ')||(chars[index]=='='&& chars[index +1]!='\''&& chars[index +1]!='=');while((index +1< chars.length)&& flag){
flag =(chars[index]=='='&& chars[index +1]==' ')||(chars[index]=='='&& chars[index +1]!=' ')||(chars[index]=='='&& chars[index +1]!='\''&& chars[index +1]!='=');if(flag){
appendFlag =true;
index++;}}}if(appendFlag){int arrIndex =0;for(int i =0; i < indexList.size(); i++){int value = indexList.get(i);if(value == integer){
arrIndex = i;}}if(arrIndex ==0){
builder.append(strChars,0, integer);
builder.append("==");
builder.append(strChars, index, chars.length);}else{
builder.append(strChars,0, integer +1);
builder.append("==");
builder.append(strChars, index +1, chars.length +1);}
strChars = builder.toString();}}String str = strChars;if(str.contains(" and ")){
str = str.replace(" and "," && ");}if(str.contains(" AND ")){
str = str.replace(" AND "," && ");}if(str.contains(" or ")){
str = str.replace(" or "," || ");}if(str.contains(" OR ")){
str = str.replace(" OR "," || ");}System.out.println("str："+ str);}}publicstaticvoiddealOneEqual(String where){ArrayList<Integer> indexList =newArrayList<>();String strChars = where.replaceAll(" {2,}"," ");char[] chars = strChars.toCharArray();for(int i =0; i < chars.length; i++){if(chars[i]=='='){
indexList.add(i);}}StringBuilder builder =newStringBuilder();for(Integer integer : indexList){int index = integer;boolean appendFlag =false;if(chars[index -1]!='>'&& chars[index -1]!='<'&& chars[index -1]!='!'){
appendFlag =true;boolean flag = chars[index +1]==' ';while((index +1< chars.length)&& flag){
flag = chars[index +1]==' ';if(flag){
index++;}}}if(appendFlag){
builder.append(strChars,0, integer);
builder.append("==");
builder.append(strChars, index +1, chars.length);}}System.out.println("一个等号："+ builder);}publicstaticvoiddealTwoEqual(String where){ArrayList<Integer> indexList =newArrayList<>();String strChars = where.replaceAll(" {2,}"," ");char[] chars = strChars.toCharArray();for(int i =0; i < chars.length; i++){if(chars[i]=='='){
indexList.add(i);}}StringBuilder builder =newStringBuilder();for(Integer integer : indexList){int index = integer;boolean appendFlag =false;boolean flag = chars[index +1]==' '&& chars[index +2]=='=';while((index +2< chars.length)&& flag){
flag = chars[index +1]==' '&& chars[index +2]=='=';if(flag){
appendFlag =true;
index++;}}if(appendFlag){
builder.append(strChars,0, integer);
builder.append("==");
builder.append(strChars, index +2, chars.length);}}System.out.println("两个等号："+ builder);}}
输出结果
builder：app_id==‘005’ AND keyid==‘0101’
str：app_id==‘005’ && keyid==‘0101’
经过多重测试后，发现此方案行不通，有些条件还是无法满足，比较条件超过两个，如下：
StringWHERE="app_id='005' AND keyid='0101' AND keyid='0101'";
输出结果
builder：app_id==‘005’ AND keyid==‘0101’ AND keyi==='0101
str：app_id==‘005’ && keyid==‘0101’ && keyi==='0101
第三个就会引起索引替换问题出错，变成三个等号了，没办法，只能重新修改逻辑，继续改善。
★不推荐★
方案二
📌进阶版
针对方案一不能满足多个条件替换的问题，我们对替换拼接的索引改成了动态的，先看代码：
packagecom.example.business.util;importjava.util.ArrayList;/**
* @ClassName: Test
* @Description: 临时测试类
* @Author yang
* @Date 2022/12/20
* @Version 1.0
*/publicclassTest2{publicstaticvoidmain(String[] args){// String WHERE = "app_id='005' AND keyid='0101' AND keyid='0101'";//√// String WHERE = "app_id >= '005' AND keyid ='0101' AND keyid ='0101' AND keyid ='0101'";//X// String WHERE = "keyid ='0101' AND app_id >= '005' AND keyid ='0101' AND keyid ='0101'";//X// String WHERE = "keyid ='0101' AND app_id >= '005' AND app_id <= '005' AND keyid ='0101'";//X// String WHERE = "app_id >= '005' AND keyid ='0101'";//√// String WHERE = "keyid ='0101' AND app_id >= '005'";//√// String WHERE = "keyid ='0101' AND keyid ='0101' AND app_id >= '005'";//√// String WHERE = "pay_time >=2019/10/21 and pay_time <= 2019/10/22 and app_id = 001";//X// String WHERE = "pay_time >='2019/10/21' and pay_time <= '2019/10/22' and app_id = '001'";//X// String WHERE = "app_id=005 AND keyid=0101";//√// String WHERE = "app_id= 005 AND keyid = 0101";//√StringWHERE="app_id= 005 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101";//√// String WHERE = "app_id>= 005 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101";//X// String WHERE = "app_id >= 005 AND keyid = 0101";//X// String WHERE = "app_id >= 005 AND app_id <= 005 AND keyid = 0101 AND keyid = 0105";//X// String WHERE = "keyid = 0101 AND keyid = 0105";//√// String WHERE = "app_id=005";//√// String WHERE = "app_id!=005";if(WHERE.contains("\'")){//去除字符串多余空格，只能存在一个空格（即把两个以上的空格替换成一个）ArrayList<Integer> indexList =newArrayList<>();String strChars =WHERE.replaceAll(" {2,}"," ");if(strChars.contains("> =")|| strChars.contains("< =")|| strChars.contains("! =")|| strChars.contains("= =")|| strChars.contains("==")){System.out.println("sql语句格式错误，注意比较符（>=、<=、!=）中间不允许出现空格，不能出现两个等号（==）");return;}char[] chars = strChars.toCharArray();for(int i =0; i < chars.length; i++){if(chars[i]=='='){
indexList.add(i);}}boolean sign =false;boolean num =false;for(Integer integer : indexList){StringBuilder builder =newStringBuilder();int index = integer;boolean appendFlag =false;if(chars[index -1]!='>'&& chars[index -1]!='<'&& chars[index -1]!='!'){boolean flag = chars[index]=='=';while((index +1< chars.length)&& flag){
flag = chars[index]=='=';if(flag){
appendFlag =true;
index++;}}}else{
sign =true;}// if (sign) {// builder.append(strChars, 0, integer); builder.append("==");// builder.append(strChars, index, chars.length);// strChars = builder.toString();// }if(appendFlag){int arrIndex =0;for(int i =0; i < indexList.size(); i++){int value = indexList.get(i);if(value == integer){
arrIndex = i;}}int sum =0;char[] chars2 = strChars.toCharArray();if(arrIndex ==0){
builder.append(strChars,0, integer);
builder.append("==");
builder.append(strChars, index, chars.length);}elseif(arrIndex >0&& sign){
builder.append(strChars,0, integer);
builder.append("==");
builder.append(strChars, index, chars.length);
sign =false;
num =true;}elseif(arrIndex >0&&!sign && num){
builder.append(strChars,0, integer +1);
builder.append("==");
builder.append(strChars, index +1, chars.length +1);
num =false;}else{
builder.append(strChars,0, integer + arrIndex);
builder.append("==");
builder.append(strChars, index + arrIndex, chars.length + arrIndex);}
strChars = builder.toString();}}// System.out.println("builder：" + strChars);String str = strChars.toLowerCase();if(str.contains(" and ")){
str = str.replace(" and "," && ");}if(str.contains(" or ")){
str = str.replace(" or "," || ");}System.out.println("str："+ str);}else{//去除字符串多余空格，只能存在一个空格（即把两个以上的空格替换成一个）ArrayList<Integer> indexList =newArrayList<>();String strChars =WHERE.replaceAll(" {2,}"," ");if(strChars.contains("> =")|| strChars.contains("< =")|| strChars.contains("! =")|| strChars.contains("= =")|| strChars.contains("==")){System.out.println("sql语句格式错误，注意比较符（>=、<=、!=）中间不允许出现空格，不能出现两个等号（==）");return;}char[] chars = strChars.toCharArray();for(int i =0; i < chars.length; i++){if(chars[i]=='='){
indexList.add(i);}}for(Integer integer : indexList){StringBuilder builder =newStringBuilder();int index = integer;boolean appendFlag =false;if(chars[index -1]!='>'&& chars[index -1]!='<'&& chars[index -1]!='!'){boolean flag = chars[index]=='=';while((index +1< chars.length)&& flag){
flag = chars[index]=='=';if(flag){
appendFlag =true;
index++;}}}if(appendFlag){int arrIndex =0;for(int i =0; i < indexList.size(); i++){int value = indexList.get(i);if(value == integer){
arrIndex = i;}}char[] chars2 = strChars.toCharArray();if(arrIndex ==0){
builder.append(strChars,0, integer);
builder.append("==");
builder.append(strChars, index, chars.length);}else{
builder.append(strChars,0, integer + arrIndex);
builder.append("==");
builder.append(strChars, index + arrIndex, chars.length + arrIndex);}
strChars = builder.toString();}}String str = strChars.toLowerCase();if(str.contains(" and ")){
str = str.replace(" and "," && ");}if(str.contains(" or ")){
str = str.replace(" or "," || ");}System.out.println("str："+ str);}}}
先看结果：
输出结果
str：app_id== 005 && keyid == 0101 && keyid == 0101 && keyid == 0101 && keyid == 0101 && keyid == 0101 && keyid == 0101 && keyid == 0101
发现可以解决方案一的问题。可是，随着慢慢的测试，bug还是出现了。比如条件中不是单纯的等号，而是包含大于等于、小于等于（>=、<=）等等情况，就会抛索引越界异常。如下：
StringWHERE="app_id >= '005' AND keyid ='0101' AND keyid ='0101' AND keyid ='0101'";
输出结果
Exception in thread “main” java.lang.IndexOutOfBoundsException: start 66, end 72, s.length() 71
at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:539)
at java.lang.StringBuilder.append(StringBuilder.java:175)
at com.example.business.util.Test2.main(Test2.java:102)
经过多重的调试，发现根据这个where语句的判断是存在很多问题，很多种时候，空格也是导致判断条件出现漏判，是行不通的，很多种多重条件，无法同时兼容，最后参考sql的语法，决定对目标where进行一下限定判断，即（比较符（>=、<=、!=、<>）中间不允许出现空格，不能出现两个等号（==或= =））
如果是这样，那逻辑就会容易很多了，我们可以忽略比较符（>=、<=、!=、<>）中间出现空格的问题，以及两个等号（==或= =））的问题，这样，我们可以直接根据等号（=）进行分割，对分割后的数组进行判断拼接。详细代码请看方案三。
★不推荐★
方案三
📌终极版
总结了方案一和方案二出现的各种问题，对原先的代码进行了重构，先看代码：
packagecom.example.business.util;importjava.util.Arrays;importjava.util.HashMap;importjava.util.Map;importjava.util.regex.Matcher;importjava.util.regex.Pattern;/**
* @ClassName: Test
* @Description: 临时测试类
* @Author yang
* @Date 2022/12/20
* @Version 1.0
*/publicclassTest3{publicstaticvoidmain(String[] args){// String WHERE = "app_id='005' AND keyid='0101' AND keyid='0101'";//√// String WHERE = "app_id >= '005' AND keyid ='0101' AND keyid ='0101' AND keyid ='0101'";//// String WHERE = "keyid ='0101' AND app_id <> '005' AND keyid <>'0101' AND keyid ='0101'";//XStringWHERE="keyid ='0101' AND app_id >= '005' AND app_id <= '005' AND keyid ='0101'";//X// String WHERE = "app_id >= '005' AND keyid ='0101'";//√// String WHERE = "keyid ='0101' AND app_id >= '005'";//√// String WHERE = "keyid ='0101' AND keyid ='0101' AND app_id >= '005'";//√// String WHERE = "pay_time >=2019/10/21 and pay_time <= 2019/10/22 and app_id = 001";//X// String WHERE = "pay_time >='2019/10/21' and pay_time <= '2019/10/22' and app_id = '001'";//X// String WHERE = "app_id=005 AND keyid=0101";//√// String WHERE = "app_id= 005 AND keyid = 0101";//√// String WHERE = "app_id= 005 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101";//√// String WHERE = "app_id>= 005 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101";//X// String WHERE = "app_id >= 005 AND keyid = 0101";//X// String WHERE = "app_id >= 005 AND app_id <= 005 AND keyid = 0101 AND keyid = 0105";//X// String WHERE = "keyid = 0101 AND keyid = 0105";//√// String WHERE = "app_id=005";//√// String WHERE = "app_id!=005";// String WHERE = "app_id< >005";// String WHERE = "app_id< =005";// String WHERE = "app_id> =005";// String WHERE = "app_id>005";// String WHERE = "app_id>=005 and app_id BETWEEN '2018-06-28' AND '2018-09-28'";// String WHERE = "app_id like '2018-09-28'";// String WHERE = "app_id in (1,2) and a=8";// String WHERE = "app_id in (1,2) and a>=8";// String WHERE = "app_id<005 and appid=005 or key=50 and a>=10 or b<=50 and c!=6";// String WHERE = "app_id BETWEEN '2018-06-28' AND '2018-09-28' and appid=005 or key=50 and a>=10 or b<=50 and c!=6;";// String WHERE = "app_id like '2018-09-28' and appid=005 or key=50 and a>=10 or b<=50 and c!=6;";// String WHERE = "app_id in (1,2) and appid=005 or key=50 and a>=10 or b<=50 and c!=6;";WHERE=WHERE.toLowerCase();String strChars =WHERE.replaceAll(" {2,}"," ");if(strChars.contains("> =")|| strChars.contains("< =")|| strChars.contains("! =")|| strChars.contains("< >")|| strChars.contains("= =")|| strChars.contains("==")){System.out.println("sql语句格式错误，注意比较符（>=、<=、!=、<>）中间不允许出现空格，不能出现两个等号（==或= =）");return;}String[] arr = strChars.split("=");System.out.println(Arrays.toString(arr));StringBuilder str =newStringBuilder();for(int i =0; i < arr.length; i++){String a = arr[i];if(!a.contains("<")&&!a.contains(">")&&!a.contains("!")&&!(i == arr.length -1)){
str.append(a +"==");}elseif(i == arr.length -1){
str.append(a);}elseif(a.contains("<>")){
str.append(a +"==");}else{
str.append(a +"=");}}String strWhere = str.toString().replace("<>","!=");System.out.println(strWhere);if(strWhere.contains(" and ")){
strWhere = strWhere.replace(" and "," && ");}if(strWhere.contains(" or ")){
strWhere = strWhere.replace(" or "," || ");}System.out.println(strWhere);}}
输出结果
[keyid , ‘0101’ and app_id >, ‘005’ and app_id <, ‘005’ and keyid , ‘0101’]
keyid ==‘0101’ and app_id >= ‘005’ and app_id <= ‘005’ and keyid ==‘0101’
keyid ==‘0101’ && app_id >= ‘005’ && app_id <= ‘005’ && keyid ==‘0101’
原本以为方案三已经完成所有需求，结果经过多种运算符的测试时，还是发现有个bug，就是只有一个大于号或者小于号（< 、>）时，拼接会有问题，如下：
StringWHERE="app_id<005 and appid=005 or key=50 and a>=10 or b<=50 and c!=6";
输出结果
[app_id<005 and appid, 005 or key, 50 and a>, 10 or b<, 50 and c!, 6]
app_id<005 and appid=005 or key50 and a>=10 or b<=50 and c!=6
app_id<005 && appid=005 || key50 && a>=10 || b<=50 && c!=6
经过Debug调试发现，只有一个只有一个大于号或者小于号（< 、>）时，直接走的是else的判断，就拼了一个等号（=），明显是不符合要求的，那么怎么去实现这个bug吗？经过细心观察，发现了一个特点，就是以等号（=）分割后，每段字符后面如果不是特殊字符，即不是大于号、小于号和叹号（< 、>、!）时，是需要拼接两个等号（==）的，这样才符合前面的需求。所以，对else部分的代码又进行了一层代码，详情请往下看。
★不推荐★
方案四
📌标准版
针对方案三出现的bug，排查发现，是漏掉了一个判断限定条件，即分割后的每段字符串，我们应该检验一下它的最后一个字符，是不是特殊字符（即是否包含 <、>、 !）。
packagecom.example.business.util;importjava.util.Arrays;importjava.util.regex.Matcher;importjava.util.regex.Pattern;/**
* @ClassName: Test
* @Description: 临时测试类
* @Author yang
* @Date 2022/12/20
* @Version 1.0
*/publicclassTest3{publicstaticvoidmain(String[] args){// String WHERE = "app_id='005' AND keyid='0101' AND keyid='0101'";//√// String WHERE = "app_id >= '005' AND keyid ='0101' AND keyid ='0101' AND keyid ='0101'";//// String WHERE = "keyid ='0101' AND app_id <> '005' AND keyid <>'0101' AND keyid ='0101'";//X// String WHERE = "keyid ='0101' AND app_id >= '005' AND app_id <= '005' AND keyid ='0101'";//X// String WHERE = "app_id >= '005' AND keyid ='0101'";//√// String WHERE = "keyid ='0101' AND app_id >= '005'";//√// String WHERE = "keyid ='0101' AND keyid ='0101' AND app_id >= '005'";//√// String WHERE = "pay_time >=2019/10/21 and pay_time <= 2019/10/22 and app_id = 001";//X// String WHERE = "pay_time >='2019/10/21' and pay_time <= '2019/10/22' and app_id = '001'";//X// String WHERE = "app_id=005 AND keyid=0101";//√// String WHERE = "app_id= 005 AND keyid = 0101";//√// String WHERE = "app_id= 005 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101";//√// String WHERE = "app_id>= 005 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101";//X// String WHERE = "app_id >= 005 AND keyid = 0101";//X// String WHERE = "app_id >= 005 AND app_id <= 005 AND keyid = 0101 AND keyid = 0105";//X// String WHERE = "keyid = 0101 AND keyid = 0105";//√// String WHERE = "app_id=005";//√// String WHERE = "app_id!=005";// String WHERE = "app_id< >005";// String WHERE = "app_id< =005";// String WHERE = "app_id> =005";// String WHERE = "app_id>005";// String WHERE = "app_id>=005 and app_id BETWEEN '2018-06-28' AND '2018-09-28'";// String WHERE = "app_id like '2018-09-28'";// String WHERE = "app_id in (1,2) and a=8";// String WHERE = "app_id in (1,2) and a>=8";StringWHERE="app_id<005 and appid=005 or key=50 and a>=10 or b<=50 and c!=6";// String WHERE = "app_id BETWEEN '2018-06-28' AND '2018-09-28' and appid=005 or key=50 and a>=10 or b<=50 and c!=6;";// String WHERE = "app_id like '2018-09-28' and appid=005 or key=50 and a>=10 or b<=50 and c!=6;";// String WHERE = "app_id in (1,2) and appid=005 or key=50 and a>=10 or b<=50 and c!=6;";WHERE=WHERE.toLowerCase();String strChars =WHERE.replaceAll(" {2,}"," ");if(strChars.contains("> =")|| strChars.contains("< =")|| strChars.contains("! =")|| strChars.contains("< >")|| strChars.contains("= =")|| strChars.contains("==")){System.out.println("sql语句格式错误，注意比较符（>=、<=、!=、<>）中间不允许出现空格，不能出现两个等号（==或= =）");return;}String[] arr = strChars.split("=");System.out.println(Arrays.toString(arr));StringBuilder str =newStringBuilder();for(int i =0; i < arr.length; i++){String a = arr[i];if(!a.contains("<")&&!a.contains(">")&&!a.contains("!")&&!(i == arr.length -1)){
str.append(a +"==");}elseif(i == arr.length -1){
str.append(a);}elseif(a.contains("<>")){
str.append(a +"==");}else{String last = a.substring(a.length()-1);if(!(isSpecialChar(last))){
str.append(a +"==");}else{
str.append(a +"=");}}}String strWhere = str.toString().replace("<>","!=");System.out.println(strWhere);if(strWhere.contains(" and ")){
strWhere = strWhere.replace(" and "," && ");}if(strWhere.contains(" or ")){
strWhere = strWhere.replace(" or "," || ");}System.out.println(strWhere);}publicstaticbooleanisSpecialChar(String str){String regEx ="[ _`~!@#$%^&*()+=|{}':;',\\[\\].<>/?~！@#￥%……&*（）——+|{}【】‘；：”“’。，、？]|\n|\r|\t";Pattern p =Pattern.compile(regEx);Matcher m = p.matcher(str);return m.find();}}
输出结果
[app_id<005 and appid, 005 or key, 50 and a>, 10 or b<, 50 and c!, 6]
app_id<005 and appid005 or key50 and a>=10 or b<=50 and c!=6
app_id<005 && appid005 || key50 && a>=10 || b<=50 && c!=6
经过了上面的多种条件测试，我能想到的sql语法的都测试了，暂时没有发现问题。
★推荐★
附 JexlEngine 方法
/**
* 这个方法能够将字符串当作java代码来执行
*
* @param express
* @return
*/publicstaticObjectexecuteString(String express,Map<String,Object> parameter){JexlEngine jexlEngine =newJexlEngine();Expression expression;try{
expression = jexlEngine.createExpression(express);//将参数中的字符串传进来}catch(Exception e){thrownewJexlException(null,"Jexl异常");}JexlContext jexlContext =newMapContext();for(String key : parameter.keySet()){//遍历传过来的参数
jexlContext.set(key, parameter.get(key));//将传进来的参数替换到表达式中去}if(null== expression.evaluate(jexlContext)){//执行表达式return"";//为空就返回空字符串}return expression.evaluate(jexlContext);//执行表达式，返回结果}
完整测试源码：
packagecom.example.business.util;importjava.util.Arrays;importjava.util.HashMap;importjava.util.Map;importjava.util.regex.Matcher;importjava.util.regex.Pattern;/**
* @ClassName: Test
* @Description: 临时测试类
* @Author yang
* @Date 2022/12/20
* @Version 1.0
*/publicclassTest3{publicstaticvoidmain(String[] args){// String WHERE = "app_id='005' AND keyid='0101' AND keyid='0101'";//√// String WHERE = "app_id >= '005' AND keyid ='0101' AND keyid ='0101' AND keyid ='0101'";//// String WHERE = "keyid ='0101' AND app_id <> '005' AND keyid <>'0101' AND keyid ='0101'";//X// String WHERE = "keyid ='0101' AND app_id >= '005' AND app_id <= '005' AND keyid ='0101'";//X// String WHERE = "app_id >= '005' AND keyid ='0101'";//√// String WHERE = "keyid ='0101' AND app_id >= '005'";//√// String WHERE = "keyid ='0101' AND keyid ='0101' AND app_id >= '005'";//√// String WHERE = "pay_time >=2019/10/21 and pay_time <= 2019/10/22 and app_id = 001";//X// String WHERE = "pay_time >='2019/10/21' and pay_time <= '2019/10/22' and app_id = '001'";//X// String WHERE = "app_id=005 AND keyid=0101";//√// String WHERE = "app_id= 005 AND keyid = 0101";//√// String WHERE = "app_id= 005 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101";//√// String WHERE = "app_id>= 005 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101 AND keyid = 0101";//X// String WHERE = "app_id >= 005 AND keyid = 0101";//X// String WHERE = "app_id >= 005 AND app_id <= 005 AND keyid = 0101 AND keyid = 0105";//X// String WHERE = "keyid = 0101 AND keyid = 0105";//√// String WHERE = "app_id=005";//√// String WHERE = "app_id!=005";// String WHERE = "app_id< >005";// String WHERE = "app_id< =005";// String WHERE = "app_id> =005";// String WHERE = "app_id>005";// String WHERE = "app_id>=005 and app_id BETWEEN '2018-06-28' AND '2018-09-28'";// String WHERE = "app_id like '2018-09-28'";// String WHERE = "app_id in (1,2) and a=8";// String WHERE = "app_id in (1,2) and a>=8";StringWHERE="app_id<005 and appid=005 or key=50 and a>=10 or b<=50 and c!=6";// String WHERE = "app_id BETWEEN '2018-06-28' AND '2018-09-28' and appid=005 or key=50 and a>=10 or b<=50 and c!=6;";// String WHERE = "app_id like '2018-09-28' and appid=005 or key=50 and a>=10 or b<=50 and c!=6;";// String WHERE = "app_id in (1,2) and appid=005 or key=50 and a>=10 or b<=50 and c!=6;";WHERE=WHERE.toLowerCase();String strChars =WHERE.replaceAll(" {2,}"," ");if(strChars.contains("> =")|| strChars.contains("< =")|| strChars.contains("! =")|| strChars.contains("< >")|| strChars.contains("= =")|| strChars.contains("==")){System.out.println("sql语句格式错误，注意比较符（>=、<=、!=、<>）中间不允许出现空格，不能出现两个等号（==或= =）");return;}String[] arr = strChars.split("=");System.out.println(Arrays.toString(arr));StringBuilder str =newStringBuilder();for(int i =0; i < arr.length; i++){String a = arr[i];if(!a.contains("<")&&!a.contains(">")&&!a.contains("!")&&!(i == arr.length -1)){
str.append(a +"==");}elseif(i == arr.length -1){
str.append(a);}elseif(a.contains("<>")){
str.append(a +"==");}else{String last = a.substring(a.length()-1);if(!(isSpecialChar(last))){
str.append(a +"==");}else{
str.append(a +"=");}}}String strWhere = str.toString().replace("<>","!=");System.out.println(strWhere);if(strWhere.contains(" and ")){
strWhere = strWhere.replace(" and "," && ");}if(strWhere.contains(" or ")){
strWhere = strWhere.replace(" or "," || ");}System.out.println(strWhere);// 测试功能Map<String,Object> map =newHashMap<>();
map.put("keyid","0101");
map.put("app_id","006");Object o =StringVerifyUtil.executeString("keyid =='0101' and app_id != '005'", map);System.out.println(o);}publicstaticbooleanisSpecialChar(String str){String regEx ="[ _`~!@#$%^&*()+=|{}':;',\\[\\].<>/?~！@#￥%……&*（）——+|{}【】‘；：”“’。，、？]|\n|\r|\t";Pattern p =Pattern.compile(regEx);Matcher m = p.matcher(str);return m.find();}}
输出结果
[app_id<005 and appid, 005 or key, 50 and a>, 10 or b<, 50 and c!, 6]
app_id<005 and appid005 or key50 and a>=10 or b<=50 and c!=6
app_id<005 && appid005 || key50 && a>=10 || b<=50 && c!=6
true
结语
这种处理where语句的，涉及到的各种写法实在是太多了，光是前面写逻辑都写了不少于10个版本，种种问题都是警告种种测试才发现，很难一步到位写好整个逻辑判断。（在此说明：此种做法是根据某些场景的特殊需求，迫不得已才去做。实际中应该没有几个人会有这样的需求。）原来以为在Java中能找到合适的数据库对象类处理，奈何没有找到（如果有知道的，欢迎评论区不吝指教）。
归根结底就是使用JexlEngine这个类（能将字符转成Java代码运行），它不认sql的一个等号（=），必须是两个等号（==）才行，而且AND连接语句也不能是大写，要小写and，这里建议转（&&），or 转（||）。
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本文转载自: https://blog.csdn.net/weixin_44563573/article/details/128632746
版权归原作者 程序yang 所有， 如有侵权，请联系我们删除。
版权归原作者 程序yang 所有， 如有侵权，请联系我们删除。