本文將介紹使用Java解析json和生成json,解析xml以及生成xml的一些方法。

前提摘要：JSON和XML 必須知道的傳輸格式.

JSON是什么？

JSON(JavaScript Object Notation) 是一種輕量級的數(shù)據(jù)交換格式。

• 對象示例

{
 "firstName":"Brett",
 "lastName":"McLaughlin", 
 "email":"aaaa"
}

{
    "people":[
        {"firstName":"Brett","lastName":"McLaughlin","email":"aaaa"},
        {"firstName":"Jason","lastName":"Hunter","email":"bbbb"},
        {"firstName":"Elliotte","lastName":"Harold","email":"cccc"}
    ]
}

映射的對象

源碼在[^1]菜鳥筆記Github。

public class UserModel {
    private String firstName;
    private String lastName;
    private String email;

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
}

使用[^2]fastjosn解析String

    /**
     * java-object as json-string
     * 
     * @param object
     * @return
     */
    public String seriazileAsString(Object object) {
        if (object == null) {
            return "";
        }
        try {
            return JSON.toJSONString(object, features);
        } catch (Exception ex) {
            throw new SerializationException("Could not write JSON: "
                    + ex.getMessage(), ex);
        }
    }

Object to String

    /**
     * json-string to java-object
     * 
     * @param jsonString
     * @return
     */
    public <T> T deserializeAsObject(String jsonString, Type clazz) {
        if (jsonString == null || clazz == null) {
            return null;
        }
        try {
            return JSON.parseObject(jsonString, clazz);
        } catch (Exception ex) {
            throw new SerializationException("Could not write JSON: "
                    + ex.getMessage(), ex);
        }
    }

執(zhí)行測試

mvn test -Dtest=JsonUtilTest#testJsonObject

XML[^3]是什么？

可擴展標記語言（英語：Extensible Markup Language，簡稱：XML），是一種標記語言。標記指計算機所能理解的信息符號，通過此種標記，計算機之間可以處理包含各種信息的文章等。如何定義這些標記，既可以選擇國際通用的標記語言，比如HTML，也可以使用像XML這樣由相關(guān)人士自由決定的標記語言，這就是語言的可擴展性。XML是從標準通用標記語言（SGML）中簡化修改出來的。它主要用到的有可擴展標記語言、可擴展樣式語言（XSL）、XBRL和XPath等。

Tip:xml使用非常廣，數(shù)據(jù)傳輸(API),數(shù)據(jù)存儲(Evernote導出格式),配置文件(Spring Application.xml)。

JAXB實現(xiàn) 對象的序列化和反序列化

映射的對象 XmlUserModel

@XmlRootElement
public class XmlUserModel {
    private int id;
    private String firstName;
    private String lastName;
    private String email;

    public String getEmail() {
        return email;
    }

    @XmlElement
    public void setEmail(String email) {
        this.email = email;
    }

    public String getFirstName() {
        return firstName;
    }

    @XmlElement
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public int getId() {
        return id;
    }

    @XmlAttribute
    public void setId(int id) {
        this.id = id;
    }

    public String getLastName() {
        return lastName;
    }

    @XmlElement
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
}

Object to String

    public static String seriazileAsString(Object object, Class clazz) {
        if (object == null) {
            return "";
        }
        try {
            JAXBContext jaxbContext = JAXBContext.newInstance(clazz);
            java.io.StringWriter sw = new StringWriter();

            Marshaller marshaller = jaxbContext.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            marshaller.marshal(object, sw);

            return sw.toString();
        } catch (JAXBException ex) {
            ex.printStackTrace();
        }
        return null;
    }

從XML str 解析 Object

    public static <T> T deserializeAsObject(String xmlString, Class clazz) {
        if (xmlString == null || clazz == null) {
            return null;
        }
        JAXBContext jaxbContext = null;
        try {
            jaxbContext = JAXBContext.newInstance(clazz);
            Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
            StringReader reader = new StringReader(xmlString);
            T userModel = (T) jaxbUnmarshaller.unmarshal(reader);
            return userModel;
        } catch (JAXBException e) {
            e.printStackTrace();
        }
        return null;
    }

執(zhí)行測試XmlUtilTest

mvn test -Dtest=XmlUtilTest#testXmlObject

    @Test
    public void testXmlObject() {
        XmlUserModel xmlUserModel = new XmlUserModel();
        xmlUserModel.setFirstName("chen");
        xmlUserModel.setLastName("billy");
        xmlUserModel.setEmail("wsncqs@gmail.com");
        xmlUserModel.setId(1);

        String xmlStr = XmlUtil.seriazileAsString(xmlUserModel, XmlUserModel.class);

        System.out.println(xmlStr);

        //jsonStr -> object
        XmlUserModel deXmlUserModel = XmlUtil.deserializeAsObject(xmlStr, XmlUserModel.class);

        assertEquals(xmlUserModel.getId(), deXmlUserModel.getId());
    }

生成的xml的Str如下:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xmlUserModel id="1">
    <email>wsncqs@gmail.com</email>
    <firstName>chen</firstName>
    <lastName>billy</lastName>
</xmlUserModel>

更多Xml解析閱讀推薦

• Java XML Tutorial

參考列表

• [^1]菜鳥筆記源碼
• Jackson
• Jackson 2 – Convert Java Object to / from JSON
• [^2]fastjson
• Gson
• [^3]XML WIKI
• Java XML Tutorial
• JAXB
• SAX
• dom4j

本文源代碼地址:https://github.com/daimaniu/cainiaobiji ,歡迎star 和 fork。

下期預告

下期預告(9月19號):Java常見的加密編碼學習。

歡迎大家關(guān)注我，周更兩篇Java技術(shù)文章。菜鳥筆記 下周一不見不散