菜鸟笔记(五) - 常见传输格式解析

本文将介绍使用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 必须知道的传输格式.

JSON是什么？

JSON(JavaScript Object Notation) 是一种轻量级的数据交换格式。

• 对象示例

{
 "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"}
    ]
}

映射的对象

源码在[^1]菜鸟笔记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 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);
        }
    }

执行测试

mvn test -Dtest=JsonUtilTest#testJsonObject

XML[^3]是什么？

可扩展标记语言（英语：Extensible Markup Language，简称：XML），是一种标记语言。标记指计算机所能理解的信息符号，通过此种标记，计算机之间可以处理包含各种信息的文章等。如何定义这些标记，既可以选择国际通用的标记语言，比如HTML，也可以使用像XML这样由相关人士自由决定的标记语言，这就是语言的可扩展性。XML是从标准通用标记语言（SGML）中简化修改出来的。它主要用到的有可扩展标记语言、可扩展样式语言（XSL）、XBRL和XPath等。

Tip:xml使用非常广，数据传输(API),数据存储(Evernote导出格式),配置文件(Spring Application.xml)。

JAXB实现 对象的序列化和反序列化

映射的对象 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;
    }

从XML str 解析 Object

    public static  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;
    }

执行测试XmlUtilTest

mvn test -Dtest=XmlUtilTest#testXmlObject

    @Test
    public void testXmlObject() {
        XmlUserModel xmlUserModel = new XmlUserModel();
        xmlUserModel.setFirstName("chen");
        xmlUserModel.setLastName("billy");
        xmlUserModel.setEmail("[email protected]");
        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:

    [email protected]
    chen
    billy

更多Xml解析阅读推荐

• Java XML Tutorial

参考列表

• [^1]菜鸟笔记源码
• Jackson
• Jackson 2 – Convert Java Object to / from JSON
• [^2]fastjson
• Gson
• [^3]XML WIKI
• Java XML Tutorial
• JAXB
• SAX
• dom4j

本文源代码地址:https://github.com/daimaniu/cainiaobiji ,欢迎star 和 fork。

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