Spring之Jackson–转换XML与Java对象的方法

简介

本文介绍使用Spring自带的Jackson转换XML与Java对象的方法。

XML与Java对象转换的方法有很多，最好的方法是使用Spring自带的XmlMapper，本文介绍此工具的用法。

XmlMapper类是 ObjectMapper类的子类，两者使用方式几乎一致。

依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-xml</artifactId>
    <!-- 版本由spring-boot-starter-parent指定-->
</dependency>

jackson-dataformat-xml依赖了jackson-core、jackson-databind、jackson-annotations等，这些都在spring-boot-starter-web中引入了。

整个pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.13</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.knife</groupId>
    <artifactId>Demo_XML_SpringBoot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Demo_XML_SpringBoot</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.dataformat</groupId>
            <artifactId>jackson-dataformat-xml</artifactId>
        </dependency>

        <dependency>
            <groupId>com.github.xiaoymin</groupId>
            <artifactId>knife4j-spring-boot-starter</artifactId>
            <version>3.0.3</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.24</version>
            <scope>provided</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

工具类

package com.knife.example.common.util;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.MapperFeature;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.deser.std.DateDeserializers;
import com.fasterxml.jackson.databind.ser.std.DateSerializer;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;
import com.fasterxml.jackson.dataformat.xml.ser.ToXmlGenerator;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateDeserializer;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalTimeDeserializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateSerializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;
import com.fasterxml.jackson.datatype.jsr310.ser.LocalTimeSerializer;
import lombok.SneakyThrows;

import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import java.util.Date;

public class XmlUtil {
    private static final XmlMapper xmlMapper = createXmlMapper();

    private static XmlMapper createXmlMapper() {
        XmlMapper xmlMapper = XmlMapper.builder()
                // // 忽略实体类没有对应属性。如果为 true 会抛出异常
                // .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES,false)
                // // 忽略null
                // .serializationInclusion(JsonInclude.Include.NON_NULL)
                // // 属性使用 驼峰首字母小写
                // .propertyNamingStrategy(PropertyNamingStrategy.LOWER_CAMEL_CASE)
                // .defaultUseWrapper(false)
                .build();

        // 序列化时加上文件头信息
        xmlMapper.configure(ToXmlGenerator.Feature.WRITE_XML_DECLARATION, true);
        // 美化输出结果（给XML添加缩进）
        xmlMapper.enable(SerializationFeature.INDENT_OUTPUT);

        // 把“忽略重复的模块注册”禁用，否则下面的注册不生效
        xmlMapper.disable(MapperFeature.IGNORE_DUPLICATE_MODULE_REGISTRATIONS);
        xmlMapper.registerModule(configTimeModule());
        // 重新设置为生效，避免被其他地方覆盖
        xmlMapper.enable(MapperFeature.IGNORE_DUPLICATE_MODULE_REGISTRATIONS);

        return xmlMapper;
    }

    private static JavaTimeModule configTimeModule() {
        JavaTimeModule javaTimeModule = new JavaTimeModule();

        String localDateTimeFormat = "yyyy-MM-dd HH:mm:ss";
        String localDateFormat = "yyyy-MM-dd";
        String localTimeFormat = "HH:mm:ss";
        String dateFormat = "yyyy-MM-dd HH:mm:ss";

        // 序列化
        javaTimeModule.addSerializer(
                LocalDateTime.class,
                new LocalDateTimeSerializer(DateTimeFormatter.ofPattern(localDateTimeFormat)));
        javaTimeModule.addSerializer(
                LocalDate.class,
                new LocalDateSerializer(DateTimeFormatter.ofPattern(localDateFormat)));
        javaTimeModule.addSerializer(
                LocalTime.class,
                new LocalTimeSerializer(DateTimeFormatter.ofPattern(localTimeFormat)));
        javaTimeModule.addSerializer(
                Date.class,
                new DateSerializer(false, new SimpleDateFormat(dateFormat)));

        // 反序列化
        javaTimeModule.addDeserializer(
                LocalDateTime.class,
                new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern(localDateTimeFormat)));
        javaTimeModule.addDeserializer(
                LocalDate.class,
                new LocalDateDeserializer(DateTimeFormatter.ofPattern(localDateFormat)));
        javaTimeModule.addDeserializer(
                LocalTime.class,
                new LocalTimeDeserializer(DateTimeFormatter.ofPattern(localTimeFormat)));
        javaTimeModule.addDeserializer(Date.class, new DateDeserializers.DateDeserializer(){
            @SneakyThrows
            @Override
            public Date deserialize(JsonParser jsonParser, DeserializationContext dc){
                String text = jsonParser.getText().trim();
                SimpleDateFormat sdf = new SimpleDateFormat(dateFormat);
                return sdf.parse(text);
            }
        });

        return javaTimeModule;
    }

    public static String toXml(Object o) {
        String xml = null;
        try {
            xml = xmlMapper.writeValueAsString(o);
        } catch (JsonProcessingException e) {
            throw new RuntimeException(e);
        }
        return xml;
    }

    public static <T> T toObject(String xml, Class<T> cls) {
        T t = null;

        try {
            t = xmlMapper.readValue(xml, cls);
        } catch (JsonProcessingException e) {
            throw new RuntimeException(e);
        }

        return t;
    }
}

测试类

package com.knife.example.business.controller;

import com.knife.example.business.bo.SchoolBO;
import com.knife.example.business.bo.StudentBO;
import com.knife.example.common.util.XmlUtil;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.List;

@Api(tags = "测试XML")
@RestController
@RequestMapping("xml")
public class TestController {

    @ApiOperation("对象转XML")
    @PostMapping("toXmlString")
    public String toXmlString() {
        SchoolBO schoolBO = new SchoolBO();
        schoolBO.setSchoolId(222);
        schoolBO.setSchoolName("ABC中学");
        schoolBO.setSchoolEmail("aa@163.com");
        schoolBO.setSchoolAddress("A省B市");

        List<StudentBO> studentBOList = new ArrayList<>();
        StudentBO studentBO1 = new StudentBO();
        studentBO1.setStudentName("Tony");
        studentBO1.setCreateTime(LocalDateTime.now());

        StudentBO studentBO2 = new StudentBO();
        studentBO2.setStudentName("Peter");
        studentBO2.setCreateTime(LocalDateTime.now().plusSeconds(2));

        studentBOList.add(studentBO1);
        studentBOList.add(studentBO2);

        schoolBO.setStudentBOList(studentBOList);

        return XmlUtil.toXml(schoolBO);
    }

    @ApiOperation("XML转对象")
    @PostMapping("toObject")
    public Object toObject(String xml) {
        return XmlUtil.toObject(xml, SchoolBO.class);
    }

}

实体类

• @JacksonXmlRootElement：指定生成xml根标签的名字
  • 属性：namespace，localName
• @JacksonXmlProperty：指定包装标签名，或者指定标签内部属性名
  • 属性：namespace，localName，isAttribute(default：false)
• @JacksonXmlElementWrapper：可用于List等集合类，用来指定外围标签名
  • 属性：namespace，localName，useWrapping (default：true)
• @JacksonXmlText：指定当前这个值，没有xml标签包裹。
  • 属性：namespace，localName

顶层实体类

package com.knife.example.business.bo;

import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlElementWrapper;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;
import lombok.Data;

import java.util.List;

@Data
@JacksonXmlRootElement(localName = "school")
public class SchoolBO {
    // 可以指定XML标签的名字。若不指定，则为字段名
    @JacksonXmlProperty(localName = "SchoolName")
    private String schoolName;

    // isAttribute 设为true时，该字段做为根标签的属性
    @JacksonXmlProperty(isAttribute = true)
    private Integer schoolId;

    private String schoolEmail;

    private String schoolAddress;

    // 指定外层的XML标签名
    @JacksonXmlElementWrapper(localName = "students")
    // 指定单个元素的XML标签名
    @JacksonXmlProperty(localName = "item")
    private List<StudentBO> studentBOList;
}

子层实体类

package com.knife.example.business.bo;

import lombok.Data;

import java.time.LocalDateTime;

@Data
public class StudentBO {
    private String studentName;

    private LocalDateTime createTime;
}

测试

1.对象转XML

2.XML转对象

使用此XML测试：

<?xml version='1.0' encoding='UTF-8'?>
<school schoolId="222">
  <schoolEmail>aa@163.com</schoolEmail>
  <schoolAddress>A省B市</schoolAddress>
  <SchoolName>ABC中学</SchoolName>
  <students>
    <item>
      <studentName>Tony</studentName>
      <createTime>2023-03-06 19:46:42</createTime>
    </item>
    <item>
      <studentName>Peter</studentName>
      <createTime>2023-03-06 19:46:44</createTime>
    </item>
  </students>
</school>

结果：