Java对象、Json、Xml转换工具Jackson使用

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://www.php.cn/

所需jar包如下，按照名称搜索下载即可。

这里写图片描述

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();        }    }}

所需jar包如下，按照名称搜索下载即可。

这里写图片描述

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();        }    }}

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