Java对象、Json、Xml转换工具Jackson使用

深碍√TFBOYSˉ_ 2022-08-04 11:56 223阅读 0赞

在Java项目中將一个对象转换成一段Json格式的字符串是非常常见的，能够实现这种需求的工具包也比较多，例如Gson、JSON-lib、Jackson等等。本文主要介绍Jackson的使用，Jackson除了能实现Java对象与Json串的互转外，还能將Java对象转换为Xml格式，使用较为简单而且据说效率比较高。  
对于Jackson的jar包我们可以从maven资源库中下载：[http://mvnrepository.com/][http_mvnrepository.com]

所需jar包如下，按照名称搜索下载即可。

![这里写图片描述][20150825230232856]

接下来编写测试用例，我们需要一个java类：

package com.csii.jackson.object;
    
    public class Book{
        private String name;
        private int price;
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public int getPrice() {
            return price;
        }
        public void setPrice(int price) {
            this.price = price;
        }
        public Book() {
    
        }
        public Book(String name,int price) {
            this.name = name;
            this.price = price;
        } 
        @Override
        public String toString() { 
            return "name:" + name +"; price:" + price;
        }
    
    }

1.將Java对象转换为Json字符串：

@Test
        public void testGenJson()
        {
            ObjectMapper objMapper = new ObjectMapper();
            Book book = new Book("Think in Java",100);
            try {
                jsonGen = objMapper.getJsonFactory().createJsonGenerator(System.out,JsonEncoding.UTF8);
                jsonGen.writeObject(book);
            } catch (IOException e) { 
                e.printStackTrace();
            } 
        }

运行测试方法，控制台输出：

{"name":"Think in Java","price":100}

2.將Json字符串转为Java对象：

/* * Json转Java对象 */
        @Test
        public void testGenObjByJson()
        {
            ObjectMapper objMapper = new ObjectMapper();
            String json = "{\"name\":\"Think in Java\",\"price\":100}"; 
            try {
                Book book = objMapper.readValue(json, Book.class);
                System.out.println(book);
            } catch (IOException e) { 
                e.printStackTrace();
            }  
        }

由于我们重写了Book类的toString方法，运行测试方法，控制台输出：

name:Think in Java; price:100

3.將Java对象转为Xml格式：

/* * Java对象转xml */
        @Test
        public void testGenXml()
        {
            XmlMapper xmlMapper = new XmlMapper();
    
            Book book = new Book("Think in Java",100);
            try {
                String xmlStr =  xmlMapper.writeValueAsString(book);
                System.out.println(xmlStr);
            } catch (JsonProcessingException e) { 
                e.printStackTrace();
            }
        }

运行测试方法，控制台输出：

<Book xmlns=""><name>Think in Java</name><price>100</price></Book>

4.將xml格式字符串转为Java对象：

/* * xml转Java对象 */
        @Test
        public void testGenObjByXml()
        {
            XmlMapper xmlMapper = new XmlMapper();
            String xmlStr = "<Book><name>Think in Java</name><price>100</price></Book>"; 
            try {
                Book book = xmlMapper.readValue(xmlStr, Book.class);
                System.out.println(book);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
    
        }

输出内容：

name:Think in Java; price:100

完整的测试用例代码：

package com.csii.jackson.test;
    
    import java.io.IOException;
    
    import org.junit.Test;
    
    import com.csii.jackson.object.Book;
    import com.fasterxml.jackson.core.JsonEncoding;
    import com.fasterxml.jackson.core.JsonGenerator;
    import com.fasterxml.jackson.core.JsonProcessingException;
    import com.fasterxml.jackson.databind.ObjectMapper;
    import com.fasterxml.jackson.dataformat.xml.XmlMapper;
    @SuppressWarnings("deprecation")
    public class JsonTest { 
        private JsonGenerator jsonGen = null;
        /* * Java对象转 Json */
        @Test
        public void testGenJson()
        {
            ObjectMapper objMapper = new ObjectMapper();
            Book book = new Book("Think in Java",100);
            try {
                jsonGen = objMapper.getJsonFactory().createJsonGenerator(System.out,JsonEncoding.UTF8);
                jsonGen.writeObject(book);
            } catch (IOException e) { 
                e.printStackTrace();
            } 
        }
        /* * Json转Java对象 */
        @Test
        public void testGenObjByJson()
        {
            ObjectMapper objMapper = new ObjectMapper();
            String json = "{\"name\":\"Think in Java\",\"price\":100}"; 
            try {
                Book book = objMapper.readValue(json, Book.class);
                System.out.println(book);
            } catch (IOException e) { 
                e.printStackTrace();
            }  
        }
        /* * Java对象转xml */
        @Test
        public void testGenXml()
        {
            XmlMapper xmlMapper = new XmlMapper();
    
            Book book = new Book("Think in Java",100);
            try {
                String xmlStr =  xmlMapper.writeValueAsString(book);
                System.out.println(xmlStr);
            } catch (JsonProcessingException e) { 
                e.printStackTrace();
            }
        }
        /* * xml转Java对象 */
        @Test
        public void testGenObjByXml()
        {
            XmlMapper xmlMapper = new XmlMapper();
            String xmlStr = "<Book><name>Think in Java</name><price>100</price></Book>"; 
            try {
                Book book = xmlMapper.readValue(xmlStr, Book.class);
                System.out.println(book);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
    
        }
    }

[http_mvnrepository.com]: http://mvnrepository.com/
[20150825230232856]: /images/20220731/c702a6f5fd444679ad1f4561b37ac60c.png