背景
实际开发中，常常需要将比较复杂的 JSON 字符串转换为对应的 Java 对象。这里记录下解决方案。
如下所示，是入侵事件检测得到的 JSON 串：
[{"rule_id":"反弹shell","format_output":"进程 pname 反向连接到 %dest_ip%:%dest_port%","info":{"process_events":{"pid":21,"pname":"nginx","cmdline":"curl www.cfda.com","ppid":7,"ppname":"bash"},"proc_trees":[{"pid":21,"pname":"nginx","cmdline":"curl www.cfda.com","ppid":7,"ppname":"bash"}],"containers":{"container_id":"fef4636d8403871c2e56e06e51d609554564adbbf8284dd914a0f61130558bdf","container_name":"nginx","image_id":"4eb8f7c43909449dbad801c50d9dccc7dc86631e54f28b1a4b13575729065be8","status":"Running"},"sockets":{"src_ip":"127.0.0.1","src_port":"8080","type":"1","in_out":"0","dest_ip":"localhost","dest_port":"80"}}}]
方法
预备工作
把上述 json 串放在 src/test/resources 下，写一个文件读写程序来解析。 其实放在哪里不重要，重要的是拿到这个 JSON 串便于后续解析。
public static String readFromSource(String filename) {
try {
InputStream is = RWTool.class.getResourceAsStream(filename);
byte[] bytes = new byte[4096];
int num = 0;
String json = "";
while((num=is.read(bytes))>0){
json=new String(bytes,0,num);
}
return json;
} catch (Exception ex) {
throw new RuntimeException(ex.getCause());
}
}
构建对象模型
首先，要根据这个 JSON 字符串解析出对应的数据模型 AgentDetectEventData。主要就是按照 JSON 串中的 key 的层次结构来建立。
@Getter
@Setter
public class AgentDetectEventData {
@SerializedName("rule_id")
@JsonProperty("rule_id")
private String ruleId;
@SerializedName("format_output")
@JsonProperty("format_output")
private String formatOutput;
@SerializedName("info")
@JsonProperty("info")
private AgentDetectEventDetail info;
}
@Getter
@Setter
public class AgentDetectEventDetail {
@SerializedName("process_events")
@JsonProperty("process_events")
private ProcessEvent processEvent;
@SerializedName("proc_trees")
@JsonProperty("proc_trees")
private List<ProcessTree> procTree;
@SerializedName("containers")
@JsonProperty("containers")
private Container container;
@SerializedName("sockets")
@JsonProperty("sockets")
private Socket socket;
}
@Getter
@Setter
public class ProcessEvent {
@SerializedName("pid")
@JsonProperty("pid")
private String pid;
@SerializedName("pname")
@JsonProperty("pname")
private String pname;
@SerializedName("cmdline")
@JsonProperty("cmdline")
private String cmdline;
@SerializedName("ppid")
@JsonProperty("ppid")
private String ppid;
@SerializedName("ppname")
@JsonProperty("ppname")
private String ppname;
}
@Getter
@Setter
public class ProcessTree {
@SerializedName("pid")
@JsonProperty("pid")
private String pid;
@SerializedName("pname")
@JsonProperty("pname")
private String pname;
@SerializedName("cmdline")
@JsonProperty("cmdline")
private String cmdline;
@SerializedName("ppid")
@JsonProperty("ppid")
private String ppid;
@SerializedName("ppname")
@JsonProperty("ppname")
private String ppname;
}
@Getter
@Setter
public class Container {
@SerializedName("container_id")
@JsonProperty("container_id")
private String containerId;
@SerializedName("container_name")
@JsonProperty("container_name")
private String containerName;
@SerializedName("image_id")
@JsonProperty("image_id")
private String imageId;
@SerializedName("status")
@JsonProperty("status")
private String status;
}
@Getter
@Setter
public class Socket {
@SerializedName("src_ip")
@JsonProperty("src_ip")
private String srcIp;
@SerializedName("src_port")
@JsonProperty("src_port")
private String srcPort;
@SerializedName("type")
@JsonProperty("type")
private String type;
@SerializedName("in_out")
@JsonProperty("in_out")
private String inOut;
@SerializedName("dest_ip")
@JsonProperty("dest_ip")
private String destIp;
@SerializedName("dest_port")
@JsonProperty("dest_port")
private String destPort;
}
这里有两个注意点：
-
JSON 字符串的字段命名是下划线形式，而 Java 对象的属性命名是驼峰式的，这里需要做一个字段名映射转换。 使用 Jackson 库来转换，是 @JsonProperty 注解； 使用 gson 库来转换，是 @SerializedName 注解。
-
需要加 getter / setter 方法。
对象模型建立后，就成功了一大半。接下来，就是使用 json 库来解析了。
使用jackson 库解析
public class JsonUtil {
private static Logger logger = LoggerFactory.getLogger(JsonUtil.class);
private static final ObjectMapper MAPPER = new ObjectMapper();
static {
// 为保持对象版本兼容性,忽略未知的属性
MAPPER.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
// 序列化的时候，跳过null值
MAPPER.getSerializationConfig().setSerializationInclusion(JsonSerialize.Inclusion.NON_NULL);
// date类型转化
SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
MAPPER.setDateFormat(fmt);
}
/**
* 将一个json字符串解码为java对象
*
* 注意：如果传入的字符串为null，那么返回的对象也为null
*
* @param json json字符串
* @param cls 对象类型
* @return 解析后的java对象
* @throws RuntimeException 若解析json过程中发生了异常
*/
public static <T> T toObject(String json, Class<T> cls) {
if (json == null) {
return null;
}
try {
return MAPPER.readValue(json, cls);
} catch (Exception e) {
throw new RuntimeException(e.getCause());
}
}
public static <T> String objectToJson(T obj){
if(obj == null){
return null;
}
try {
return obj instanceof String ? (String) obj : MAPPER.writeValueAsString(obj);
} catch (Exception e) {
return null;
}
}
public static <T> T jsonToObject(String src, TypeReference<T> typeReference){
if(StringUtils.isEmpty(src) || typeReference == null){
return null;
}
try {
return (T)(typeReference.getType().equals(String.class) ? src : MAPPER.readValue(src, typeReference));
} catch (Exception e) {
logger.warn("Parse Json to Object error",e);
throw new RuntimeException(e.getCause());
}
}
public static <T> T jsonToObject(String src, Class<?> collectionClass,Class<?>... elementClasses){
JavaType javaType = MAPPER.getTypeFactory().constructParametricType(collectionClass,elementClasses);
try {
return MAPPER.readValue(src, javaType);
} catch (Exception e) {
logger.warn("Parse Json to Object error",e);
throw new RuntimeException(e.getCause());
}
}
}
单测：
public class JsonUtilTest {
@Test
public void testParseJson() {
String json = RWTool.readFromSource("/json.txt");
List<AgentDetectEventData> ade = JsonUtil.jsonToObject(json, new TypeReference<List<AgentDetectEventData>>() {});
Assert.assertNotNull(ade);
}
@Test
public void testParseJson2() {
String json = RWTool.readFromSource("/json.txt");
List<AgentDetectEventData> ade = JsonUtil.jsonToObject(json, List.class, AgentDetectEventData.class);
Assert.assertNotNull(ade);
}
}
引入POM依赖为：
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-mapper-asl</artifactId>
<version>1.9.4</version>
</dependency>
使用GSON解析
public class GsonUtil {
static GsonBuilder gsonBuilder = null;
static {
gsonBuilder = new GsonBuilder();
gsonBuilder.setDateFormat("yyyy-MM-dd HH:mm:ss");
}
public static Gson getGson() {
return gsonBuilder.create();
}
public static <T> T fromJson(String json, Class<T> cls) {
return getGson().fromJson(json, cls);
}
public static <T> T fromJson(String json, Type type) {
return getGson().fromJson(json, type);
}
}
单测：
public class GsonUtilTest {
@Test
public void testParseJson() {
String json = RWTool.readFromSource("/json.txt");
List<AgentDetectEventData> ade = GsonUtil.fromJson(json, new TypeToken<List<AgentDetectEventData>>(){}.getType());
Assert.assertNotNull(ade);
}
}
引入 POM 为：
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.3.1</version>
</dependency>
不含列表的嵌套对象
如果是不含列表的嵌套对象，则使用带 Class
@Test
public void testParseSimpleNestedJson() {
String json = "{"goods":{"desc":"2箱*250g","goodsId":8866,"orderNo":"E20210522120237009258","shopId":659494,"title":"认养一头牛"},"order":{"bookTime":1621656157,"codPay":false,"deliveryType":"express","orderNo":"E20210522120237009258","shopId":659494,"userId":1476}}";
BookInfo bookInfo = JsonUtil.toObject(json, BookInfo.class);
Assert.assertNotNull(bookInfo);
}
@Test
public void testParseSimpleNestedJson() {
String json = "{"goods":{"desc":"2箱*250g","goodsId":8866,"orderNo":"E20210522120237009258","shopId":659494,"title":"认养一头牛"},"order":{"bookTime":1621656157,"codPay":false,"deliveryType":"express","orderNo":"E20210522120237009258","shopId":659494,"userId":1476}}";
BookInfo bookInfo = GsonUtil.fromJson(json, BookInfo.class);
Assert.assertNotNull(bookInfo);
}
读者可以自行解析出 BookInfo 的对象模型。