Jsonschema2pojo从JSON生成Java类(Maven)

提示：扫一扫查出行
【扫一扫了解最新限行尾号】
复制提示

1.说明

jsonschema2pojo工具可以从JSON Schema(或示例JSON文件)生成Java类型，
并且可以配置生成Jackson 1.x,Jackson 2.x, Moshi 1.x或者Gson库的注解。
支持将jsonschema2pojo作为Maven插件、Ant任务、命令行工具、
Gradle插件或嵌入到Java应用程序中。
本文仅介绍Maven插件使用方式。
另外该工具还提供了在线版本,
可以在网站上直接使用：jsonschema2pojo online

2.创建Maven工程

Eclipse -> File -> New -> Other... -> Maven -> Maven Project
创建一个简单Maven工程，
pom.xml如下：

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>edu.yuwen.util</groupId> <artifactId>json-file</artifactId> <version>0.0.1-SNAPSHOT</version> </parent> <artifactId>generate-jsonschema2pojo</artifactId> <description>jsonschema2pojo generates Java types from JSON Schema (or example JSON)</description> </project>

3.引入Maven插件

Maven方式生成Java类需要jsonschema2pojo-maven-plugin，
在pom.xml引入这个插件：

<build> <plugins> <plugin> <groupId>org.jsonschema2pojo</groupId> <artifactId>jsonschema2pojo-maven-plugin</artifactId> <version>1.0.2</version> <configuration> <sourceDirectory>${basedir}/src/main/resources/schema</sourceDirectory> <targetPackage>com.example.types</targetPackage> </configuration> <executions> <execution> <goals> <goal>generate</goal> </goals> </execution> </executions> </plugin> </plugins> </build>

里面的配置项指定了JSON schema文件的目录，
以及生成的Java类的包路径。

4.新建JSON Schema

在src/main/resources/schema目录下
新建JSON Schema文件address.schema.json:

{ "$id": "https://example.com/address.schema.json", "$schema": "http://json-schema.org/draft-07/schema#", "description": "An address similar to http://microformats.org/wiki/h-card", "type": "object", "properties": { "post-office-box": { "type": "string" }, "extended-address": { "type": "string" }, "street-address": { "type": "string" }, "locality": { "type": "string" }, "region": { "type": "string" }, "postal-code": { "type": "string" }, "country-name": { "type": "string" } }, "required": [ "locality", "region", "country-name" ], "dependencies": { "post-office-box": [ "street-address" ], "extended-address": [ "street-address" ] } }

5.运行Maven插件

运行Maven命令，
执行插件功能：
mvn generate-sources
或者
mvn package
Maven执行成功后，
会生成target/generated-sources/jsonschema2pojo/com/example/types/Address.java类。
推荐使用mvn generate-sources，
这样生成的target目录更干净些。

6.查看Address.java

package com.example.types;import java.util.HashMap; import java.util.Map; import com.fasterxml.jackson.annotation.JsonAnyGetter; import com.fasterxml.jackson.annotation.JsonAnySetter; import com.fasterxml.jackson.annotation.JsonIgnore; import com.fasterxml.jackson.annotation.JsonInclude; import com.fasterxml.jackson.annotation.JsonProperty; import com.fasterxml.jackson.annotation.JsonPropertyOrder;/** * An address similar to http://microformats.org/wiki/h-card * */ @JsonInclude(JsonInclude.Include.NON_NULL) @JsonPropertyOrder({ "post-office-box", "extended-address", "street-address", "locality", "region", "postal-code", "country-name" }) public class AddressSchema { @JsonProperty("post-office-box") private String postOfficeBox; @JsonProperty("extended-address") private String extendedAddress; @JsonProperty("street-address") private String streetAddress; /** * * (Required) * */ @JsonProperty("locality") private String locality; /** * * (Required) * */ @JsonProperty("region") private String region; @JsonProperty("postal-code") private String postalCode; /** * * (Required) * */ @JsonProperty("country-name") private String countryName; @JsonIgnore private Map<String, Object> additionalProperties = new HashMap<String, Object>(); @JsonProperty("post-office-box") public String getPostOfficeBox() { return postOfficeBox; } @JsonProperty("post-office-box") public void setPostOfficeBox(String postOfficeBox) { this.postOfficeBox = postOfficeBox; } @JsonProperty("extended-address") public String getExtendedAddress() { return extendedAddress; } @JsonProperty("extended-address") public void setExtendedAddress(String extendedAddress) { this.extendedAddress = extendedAddress; } @JsonProperty("street-address") public String getStreetAddress() { return streetAddress; } @JsonProperty("street-address") public void setStreetAddress(String streetAddress) { this.streetAddress = streetAddress; } /** * * (Required) * */ @JsonProperty("locality") public String getLocality() { return locality; } /** * * (Required) * */ @JsonProperty("locality") public void setLocality(String locality) { this.locality = locality; } /** * * (Required) * */ @JsonProperty("region") public String getRegion() { return region; } /** * * (Required) * */ @JsonProperty("region") public void setRegion(String region) { this.region = region; } @JsonProperty("postal-code") public String getPostalCode() { return postalCode; } @JsonProperty("postal-code") public void setPostalCode(String postalCode) { this.postalCode = postalCode; } /** * * (Required) * */ @JsonProperty("country-name") public String getCountryName() { return countryName; } /** * * (Required) * */ @JsonProperty("country-name") public void setCountryName(String countryName) { this.countryName = countryName; } @JsonAnyGetter public Map<String, Object> getAdditionalProperties() { return this.additionalProperties; } @JsonAnySetter public void setAdditionalProperty(String name, Object value) { this.additionalProperties.put(name, value); } @Override public String toString() { StringBuilder sb = new StringBuilder(); sb.append(AddressSchema.class.getName()).append('@').append(Integer.toHexString(System.identityHashCode(this))).append('['); sb.append("postOfficeBox"); sb.append('='); sb.append(((this.postOfficeBox == null)?"<null>":this.postOfficeBox)); sb.append(','); sb.append("extendedAddress"); sb.append('='); sb.append(((this.extendedAddress == null)?"<null>":this.extendedAddress)); sb.append(','); sb.append("streetAddress"); sb.append('='); sb.append(((this.streetAddress == null)?"<null>":this.streetAddress)); sb.append(','); sb.append("locality"); sb.append('='); sb.append(((this.locality == null)?"<null>":this.locality)); sb.append(','); sb.append("region"); sb.append('='); sb.append(((this.region == null)?"<null>":this.region)); sb.append(','); sb.append("postalCode"); sb.append('='); sb.append(((this.postalCode == null)?"<null>":this.postalCode)); sb.append(','); sb.append("countryName"); sb.append('='); sb.append(((this.countryName == null)?"<null>":this.countryName)); sb.append(','); sb.append("additionalProperties"); sb.append('='); sb.append(((this.additionalProperties == null)?"<null>":this.additionalProperties)); sb.append(','); if (sb.charAt((sb.length()- 1)) == ',') { sb.setCharAt((sb.length()- 1), ']'); } else { sb.append(']'); } return sb.toString(); } @Override public int hashCode() { int result = 1; result = ((result* 31)+((this.postOfficeBox == null)? 0 :this.postOfficeBox.hashCode())); result = ((result* 31)+((this.streetAddress == null)? 0 :this.streetAddress.hashCode())); result = ((result* 31)+((this.postalCode == null)? 0 :this.postalCode.hashCode())); result = ((result* 31)+((this.locality == null)? 0 :this.locality.hashCode())); result = ((result* 31)+((this.countryName == null)? 0 :this.countryName.hashCode())); result = ((result* 31)+((this.additionalProperties == null)? 0 :this.additionalProperties.hashCode())); result = ((result* 31)+((this.extendedAddress == null)? 0 :this.extendedAddress.hashCode())); result = ((result* 31)+((this.region == null)? 0 :this.region.hashCode())); return result; } @Override public boolean equals(Object other) { if (other == this) { return true; } if ((other instanceof AddressSchema) == false) { return false; } AddressSchema rhs = ((AddressSchema) other); return (((((((((this.postOfficeBox == rhs.postOfficeBox)||((this.postOfficeBox!= null)&&this.postOfficeBox.equals(rhs.postOfficeBox)))&&((this.streetAddress == rhs.streetAddress)||((this.streetAddress!= null)&&this.streetAddress.equals(rhs.streetAddress))))&&((this.postalCode == rhs.postalCode)||((this.postalCode!= null)&&this.postalCode.equals(rhs.postalCode))))&&((this.locality == rhs.locality)||((this.locality!= null)&&this.locality.equals(rhs.locality))))&&((this.countryName == rhs.countryName)||((this.countryName!= null)&&this.countryName.equals(rhs.countryName))))&&((this.additionalProperties == rhs.additionalProperties)||((this.additionalProperties!= null)&&this.additionalProperties.equals(rhs.additionalProperties))))&&((this.extendedAddress == rhs.extendedAddress)||((this.extendedAddress!= null)&&this.extendedAddress.equals(rhs.extendedAddress))))&&((this.region == rhs.region)||((this.region!= null)&&this.region.equals(rhs.region)))); }}

7.引入插件依赖

当把Address.java放到工程的src/main/java目录下时，
Java编译会报错，
这是因为生成的类型依赖于Commons Lang的equals、hashCode和toString。
一些模式结构也会以Jackson注释的形式产生解析器提示。
需要在pom.xml中添加必要的依赖：

<dependencies> <dependency> <groupId>commons-lang</groupId> <artifactId>commons-lang</artifactId> <version>2.4</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.5.4</version> </dependency> </dependencies>

8.新建JSON文件

上面演示了从JSON Schema生成Java类，
下面演示从JSON文件生成Java类，
首先在src\main\resources\json目录下，
新建一个JOSN文件person.json：

{ "name":"bob", "age":33 }

9.修改插件配置

主要是指定了sourceType和sourceDirectory，
指定了源文件的格式是json和所在目录。

<build> <plugins> <plugin> <groupId>org.jsonschema2pojo</groupId> <artifactId>jsonschema2pojo-maven-plugin</artifactId> <version>1.0.2</version> <configuration> <sourceType>json</sourceType> <sourceDirectory>${basedir}/src/main/resources/json</sourceDirectory> <outputDirectory>${basedir}/src/main/java</outputDirectory> <targetPackage>com.example.types</targetPackage> <addCompileSourceRoot>true</addCompileSourceRoot> <annotationStyle>jackson2</annotationStyle> </configuration> <executions> <execution> <goals> <goal>generate</goal> </goals> </execution> </executions> </plugin> </plugins> </build>

10.生成Person.java类

mvn generate-sources执行成功后，
会生成src/main/java/com/example/types/Person.java：

11.插件配置项说明

sourceType:两个可选值，JSON Schema或者JSON文件，默认为JSON Schema。
sourceDirectory:源文件所在的目录，会将该目录下所有文件进行转换，不支持指定单个文件，如果不想全部转换，可以添加一个excludes节点。
outputDirectory:生成Java Pojo类的(根)目录，生成Java类的目录为此目录+包目录，默认值为target/generated-sources/jsonschema2pojo。
targetPackage:生成的Java pojo类的包路径。
addCompileSourceRoot:是否将输出目录作为项目的源码根目录。
annotationStyle:生成的(字段)注解样式，五个可选值：jackson1、jackson2、gson、moshi1和none，默认是jackson2，如果fastjson等工具不支持的，需要设置为none。

更多配置项的使用请参考：jsonschema2pojo-maven-plugin Optional Parameters