使用jsonpath从kettle转换json2csv

JsonPath提供的json解析非常强大，它提供了类似正则表达式的语法，基本上可以满足所有你想要获得的json内容。下面我把官网介绍的每个表达式用代码实现，可以更直观的知道该怎么用它。

一.首先需要依赖的jar包

二.因为编译的时候会报log4j的警报，所以需要在项目的src目录下新建log4j.properties文件，内容如下：

log4j.rootLogger=WARN, stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n

三.准备一个json文本

{    "store": {        "book": [            {                "category": "reference",                "author": "Nigel Rees",                "title": "Sayings of the Century",                "price": 8.95            },            {                "category": "fiction",                "author": "Evelyn Waugh",                "title": "Sword of Honour",                "price": 12.99            },            {                "category": "fiction",                "author": "Herman Melville",                "title": "Moby Dick",                "isbn": "0-553-21311-3",                "price": 8.99            },            {                "category": "fiction",                "author": "J. R. R. Tolkien",                "title": "The Lord of the Rings",                "isbn": "0-395-19395-8",                "price": 22.99            }        ],        "bicycle": {            "color": "red",            "price": 19.95        }    },    "expensive": 10}

四.我们从代码中分析用法，代码如下

package com.jsonpath;import java.io.BufferedReader;import java.io.FileNotFoundException;import java.io.FileReader;import java.util.Iterator;import java.util.List;import java.util.Map;import net.minidev.json.JSONArray;import com.jayway.jsonpath.Configuration;import com.jayway.jsonpath.JsonPath;import com.jayway.jsonpath.ReadContext;/**  * @author QiaoJiafei  * @version 创建时间：2016年3月2日 下午3:37:42  * 类说明  */public class TestJsonPath {    public static void main(String[] args) {        // TODO Auto-generated method stub        String sjson = readtxt();        //String sjson = "{\"store\": {\"book\": [{\"category\": \"reference\",\"author\": \"Nigel Rees\",\"title\": \"Sayings of the Century\",\"price\": 8.95},{\"category\": \"fiction\",\"author\": \"Evelyn Waugh\",\"title\": \"Sword of Honour\",\"price\": 12.99},{\"category\": \"fiction\",\"author\": \"Herman Melville\",\"title\": \"Moby Dick\",\"isbn\": \"0-553-21311-3\",\"price\": 8.99},{\"category\": \"fiction\",\"author\": \"J. R. R. Tolkien\",\"title\": \"The Lord of the Rings\",\"isbn\": \"0-395-19395-8\",\"price\": 22.99}],\"bicycle\": {\"color\": \"red\",\"price\": 19.95}},\"expensive\": 10}";        /*        print("--------------------------------------getJsonValue0--------------------------------------");        getJsonValue0(sjson);        print("--------------------------------------getJsonValue1--------------------------------------");        getJsonValue1(sjson);        print("--------------------------------------getJsonValue2--------------------------------------");        getJsonValue2(sjson);        print("--------------------------------------getJsonValue3--------------------------------------");        getJsonValue3(sjson);        print("--------------------------------------getJsonValue4--------------------------------------");        getJsonValue4(sjson);        */                print("--------------------------------------getJsonValue--------------------------------------");        getJsonValue(sjson);    }    private static String readtxt() {        // TODO Auto-generated method stub        StringBuilder sb = new StringBuilder();        try {            FileReader fr = new FileReader("D:/workspace/PressureTest/json.txt");            BufferedReader bfd = new BufferedReader(fr);            String s = "";            while((s=bfd.readLine())!=null) {                sb.append(s);            }        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        System.out.println(sb.toString());        return sb.toString();    }        private static void getJsonValue(String json) {        //The authors of all books：获取json中store下book下的所有author值        List<String> authors1 = JsonPath.read(json, "$.store.book[*].author");                //All authors：获取所有json中所有author的值        List<String> authors2 = JsonPath.read(json, "$..author");                //All things, both books and bicycles //authors3返回的是net.minidev.json.JSONArray：获取json中store下的所有value值，不包含key，如key有两个，book和bicycle        List<Object> authors3 = JsonPath.read(json, "$.store.*");                        //The price of everything：获取json中store下所有price的值        List<Object> authors4 = JsonPath.read(json, "$.store..price");                //The third book：获取json中book数组的第3个值        List<Object> authors5 = JsonPath.read(json, "$..book[2]");                //The first two books：获取json中book数组的第1和第2两个个值        List<Object> authors6 = JsonPath.read(json, "$..book[0,1]");                //All books from index 0 (inclusive) until index 2 (exclusive)：获取json中book数组的前两个区间值        List<Object> authors7 = JsonPath.read(json, "$..book[:2]");                //All books from index 1 (inclusive) until index 2 (exclusive)：获取json中book数组的第2个值        List<Object> authors8 = JsonPath.read(json, "$..book[1:2]");                //Last two books：获取json中book数组的最后两个值        List<Object> authors9 = JsonPath.read(json, "$..book[-2:]");                //Book number two from tail：获取json中book数组的第3个到最后一个的区间值        List<Object> authors10 = JsonPath.read(json, "$..book[2:]");                //All books with an ISBN number：获取json中book数组中包含isbn的所有值        List<Object> authors11 = JsonPath.read(json, "$..book[?(@.isbn)]");                //All books in store cheaper than 10：获取json中book数组中price<10的所有值        List<Object> authors12 = JsonPath.read(json, "$.store.book[?(@.price < 10)]");                //All books in store that are not "expensive"：获取json中book数组中price<=expensive的所有值        List<Object> authors13 = JsonPath.read(json, "$..book[?(@.price <= $['expensive'])]");                //All books matching regex (ignore case)：获取json中book数组中的作者以REES结尾的所有值（REES不区分大小写）        List<Object> authors14 = JsonPath.read(json, "$..book[?(@.author =~ /.*REES/i)]");                //Give me every thing：逐层列出json中的所有值，层级由外到内        List<Object> authors15 = JsonPath.read(json, "$..*");                //The number of books：获取json中book数组的长度        List<Object> authors16 = JsonPath.read(json, "$..book.length()");        print("**************authors1**************");        print(authors1);        print("**************authors2**************");        print(authors2);        print("**************authors3**************");        printOb(authors3);        print("**************authors4**************");        printOb(authors4);        print("**************authors5**************");        printOb(authors5);        print("**************authors6**************");        printOb(authors6);        print("**************authors7**************");        printOb(authors7);        print("**************authors8**************");        printOb(authors8);        print("**************authors9**************");        printOb(authors9);        print("**************authors10**************");        printOb(authors10);        print("**************authors11**************");        printOb(authors11);        print("**************authors12**************");        printOb(authors12);        print("**************authors13**************");        printOb(authors13);        print("**************authors14**************");        printOb(authors14);        print("**************authors15**************");        printOb(authors15);        print("**************authors16**************");        printOb(authors16);            }    /**     * 读取json的一种写法，得到匹配表达式的所有值     * */    private static void getJsonValue0(String json) {        // TODO Auto-generated method stub        List<String> authors = JsonPath.read(json, "$.store.book[*].author");        //System.out.println(authors.size());        print(authors);            }        /**     * 读取json的一种写法，得到某个具体值     * */    private static void getJsonValue1(String json) {        Object document = Configuration.defaultConfiguration().jsonProvider().parse(json);        String author0 = JsonPath.read(document, "$.store.book[0].author");        String author1 = JsonPath.read(document, "$.store.book[1].author");        print(author0);        print(author1);            }        /**     * 读取json的一种写法     * */    private static void getJsonValue2(String json) {        ReadContext ctx = JsonPath.parse(json);        List<String> authorsOfBooksWithISBN = ctx.read("$.store.book[?(@.isbn)].author");        List<Map<String, Object>> expensiveBooks = JsonPath                                    .using(Configuration.defaultConfiguration())                                    .parse(json)                                    .read("$.store.book[?(@.price > 10)]", List.class);        print(authorsOfBooksWithISBN);        print("****************Map****************");        printListMap(expensiveBooks);    }        /**     *读取json的一种写法     *得到的值是一个String，所以不能用List存储      * */    private static void getJsonValue3(String json) {        //Will throw an java.lang.ClassCastException            //List<String> list = JsonPath.parse(json).read("$.store.book[0].author");        //由于会抛异常，暂时注释上面一行，要用的话，应使用下面的格式                //Works fine        String author = JsonPath.parse(json).read("$.store.book[0].author");        print(author);    }        /**     *读取json的一种写法     *支持逻辑表达式，&&和||       * */    private static void getJsonValue4(String json) {        List<Map<String, Object>> books1 =  JsonPath.parse(json)                .read("$.store.book[?(@.price < 10 && @.category == 'fiction')]");        List<Map<String, Object>> books2 =  JsonPath.parse(json)                .read("$.store.book[?(@.category == 'reference' || @.price > 10)]");        print("****************books1****************");        printListMap(books1);        print("****************books2****************");        printListMap(books1);    }        private static void print(List<String> list) {        for(Iterator<String> it = list.iterator();it.hasNext();) {            System.out.println(it.next());        }    }        private static void printOb(List<Object> list) {        for(Iterator<Object> it = list.iterator();it.hasNext();) {            print("****");            System.out.println(it.next());        }    }        private static void printListMap(List<Map<String, Object>> list) {        for(Iterator<Map<String, Object>> it = list.iterator();it.hasNext();) {            Map<String, Object> map = it.next();            print("****");            for(Iterator iterator =map.entrySet().iterator();iterator.hasNext();) {                System.out.println(iterator.next());            }                    }    }        private static void print(String s) {        System.out.println(s);    }    }

 

1.首先我们看getJsonValue()这个方法的输出结果：

--------------------------------------getJsonValue--------------------------------------**************authors1**************Nigel ReesEvelyn WaughHerman MelvilleJ. R. R. Tolkien**************authors2**************Nigel ReesEvelyn WaughHerman MelvilleJ. R. R. Tolkien**************authors3**************[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99},{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}]{color=red, price=19.95}**************authors4**************8.9512.998.9922.9919.95**************authors5**************{category=fiction, author=Herman Melville, title=Moby Dick, isbn=0-553-21311-3, price=8.99}**************authors6**************{category=reference, author=Nigel Rees, title=Sayings of the Century, price=8.95}{category=fiction, author=Evelyn Waugh, title=Sword of Honour, price=12.99}**************authors7**************{category=reference, author=Nigel Rees, title=Sayings of the Century, price=8.95}{category=fiction, author=Evelyn Waugh, title=Sword of Honour, price=12.99}**************authors8**************{category=fiction, author=Evelyn Waugh, title=Sword of Honour, price=12.99}**************authors9**************{category=fiction, author=Herman Melville, title=Moby Dick, isbn=0-553-21311-3, price=8.99}{category=fiction, author=J. R. R. Tolkien, title=The Lord of the Rings, isbn=0-395-19395-8, price=22.99}**************authors10**************{category=fiction, author=Herman Melville, title=Moby Dick, isbn=0-553-21311-3, price=8.99}{category=fiction, author=J. R. R. Tolkien, title=The Lord of the Rings, isbn=0-395-19395-8, price=22.99}**************authors11**************{category=fiction, author=Herman Melville, title=Moby Dick, isbn=0-553-21311-3, price=8.99}{category=fiction, author=J. R. R. Tolkien, title=The Lord of the Rings, isbn=0-395-19395-8, price=22.99}**************authors12**************{category=reference, author=Nigel Rees, title=Sayings of the Century, price=8.95}{category=fiction, author=Herman Melville, title=Moby Dick, isbn=0-553-21311-3, price=8.99}**************authors13**************{category=reference, author=Nigel Rees, title=Sayings of the Century, price=8.95}{category=fiction, author=Herman Melville, title=Moby Dick, isbn=0-553-21311-3, price=8.99}**************authors14**************{category=reference, author=Nigel Rees, title=Sayings of the Century, price=8.95}**************authors15**************{book=[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99},{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}], bicycle={color=red, price=19.95}}10[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99},{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}]{color=red, price=19.95}{category=reference, author=Nigel Rees, title=Sayings of the Century, price=8.95}{category=fiction, author=Evelyn Waugh, title=Sword of Honour, price=12.99}{category=fiction, author=Herman Melville, title=Moby Dick, isbn=0-553-21311-3, price=8.99}{category=fiction, author=J. R. R. Tolkien, title=The Lord of the Rings, isbn=0-395-19395-8, price=22.99}referenceNigel ReesSayings of the Century8.95fictionEvelyn WaughSword of Honour12.99fictionHerman MelvilleMoby Dick0-553-21311-38.99fictionJ. R. R. TolkienThe Lord of the Rings0-395-19395-822.99red19.95**************authors16**************4

2.然后看getJsonValue0()、getJsonValue1()、getJsonValue2()、getJsonValue3()、getJsonValue4()的输出结果

--------------------------------------getJsonValue0--------------------------------------Nigel ReesEvelyn WaughHerman MelvilleJ. R. R. Tolkien--------------------------------------getJsonValue1--------------------------------------Nigel ReesEvelyn Waugh--------------------------------------getJsonValue2--------------------------------------Herman MelvilleJ. R. R. Tolkien****************Map********************category=fictionauthor=Evelyn Waughtitle=Sword of Honourprice=12.99****category=fictionauthor=J. R. R. Tolkientitle=The Lord of the Ringsisbn=0-395-19395-8price=22.99--------------------------------------getJsonValue3--------------------------------------Nigel Rees--------------------------------------getJsonValue4--------------------------------------****************books1********************category=fictionauthor=Herman Melvilletitle=Moby Dickisbn=0-553-21311-3price=8.99****************books2********************category=fictionauthor=Herman Melvilletitle=Moby Dickisbn=0-553-21311-3price=8.99

 3.相应的解释已经在代码中注释，更多的用法详见官网链接：https://github.com/jayway/JsonPath

4.如果只是想简单的处理json，也可以使用JSONObject和JSONArray，具体用法详见我的这篇文章：http://www.cnblogs.com/qiaoyeye/p/4730930.html

 

----------更新2016年08月19日10:06:09-------

You can use && and || to combine multiple predicates [?(@.price < 10 && @.category == 'fiction')] , [?(@.category == 'reference' || @.price > 10)]

 

这个好厉害，可以这样用

JsonPath.read(json, "$..farePrices[?(@.priceType == 'SalePrice' && @.passengerType == 'ADULT')].amount");