Java 代码精简
利用语法
利用三元表达式
普通
String title;
if (isMember(phone)) {
title = "会员";
} else {
title = "游客";
}
精简
String title = isMember(phone) ? "会员" : "游客";
利用 for-each 语句
普通
double[] values = ...;
for(int i = 0; i < values.length; i++) {
double value = values[i];
// TODO: 处理value
}
List<Double> valueList = ...;
Iterator<Double> iterator = valueList.iterator();
while (iterator.hasNext()) {
Double value = iterator.next();
// TODO: 处理value
}
精简
double[] values = ...;
for(double value : values) {
// TODO: 处理value
}
List<Double> valueList = ...;
for(Double value : valueList) {
// TODO: 处理value
}
利用 try-with-resource 语句
普通
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader("cities.csv"));
String line;
while ((line = reader.readLine()) != null) {
// TODO: 处理line
}
} catch (IOException e) {
log.error("读取文件异常", e);
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
log.error("关闭文件异常", e);
}
}
}
精简
try (BufferedReader reader = new BufferedReader(new FileReader("test.txt"))) {
String line;
while ((line = reader.readLine()) != null) {
// TODO: 处理line
}
} catch (IOException e) {
log.error("读取文件异常", e);
}
利用 return 关键字
普通
public static boolean hasSuper(@NonNull List<UserDO> userList) {
boolean hasSuper = false;
for (UserDO user : userList) {
if (Boolean.TRUE.equals(user.getIsSuper())) {
hasSuper = true;
break;
}
}
return hasSuper;
}
精简
public static boolean hasSuper(@NonNull List<UserDO> userList) {
for (UserDO user : userList) {
if (Boolean.TRUE.equals(user.getIsSuper())) {
return true;
}
}
return false;
}
利用 static 关键字
普通
public final class GisHelper {
public double distance(double lng1, double lat1, double lng2, double lat2) {
// 方法实现代码
}
}
GisHelper gisHelper = new GisHelper();
double distance = gisHelper.distance(116.178692D, 39.967115D, 116.410778D, 39.899721D);
精简
public final class GisHelper {
public static double distance(double lng1, double lat1, double lng2, double lat2) {
// 方法实现代码
}
}
double distance = GisHelper.distance(116.178692D, 39.967115D, 116.410778D, 39.899721D);
利用 lambda 表达式
普通
new Thread(new Runnable() {
public void run() {
// 线程处理代码
}
}).start();
精简
new Thread(() -> {
// 线程处理代码
}).start();
利用方法引用
普通
Arrays.sort(nameArray, (a, b) -> a.compareToIgnoreCase(b));
List<Long> userIdList = userList.stream()
.map(user -> user.getId())
.collect(Collectors.toList());
精简
Arrays.sort(nameArray, String::compareToIgnoreCase);
List<Long> userIdList = userList.stream()
.map(UserDO::getId)
.collect(Collectors.toList());
利用静态导入
普通
List<Double> areaList = radiusList.stream().map(r -> Math.PI * Math.pow(r, 2)).collect(Collectors.toList());
精简
import static java.lang.Math.PI;
import static java.lang.Math.pow;
import static java.util.stream.Collectors.toList;
List<Double> areaList = radiusList.stream().map(r -> PI * pow(r, 2)).collect(toList());
- 注意：静态引入容易造成代码阅读困难，所以在实际项目中应该警慎使用。
利用 unchecked 异常
普通
@Service
public class UserService {
public void createUser(UserCreateVO create, OpUserVO user) throws BusinessException {
checkOperatorUser(user);
...
}
private void checkOperatorUser(OpUserVO user) throws BusinessException {
if (!hasPermission(user)) {
throw new BusinessException("用户无操作权限");
}
...
}
...
}
@RestController
@RequestMapping("/user")
public class UserController {
@Autowired
private UserService userService;
@PostMapping("/createUser")
public Result<Void> createUser(@RequestBody @Valid UserCreateVO create, OpUserVO user) throws BusinessException {
userService.createUser(create, user);
return Result.success();
}
...
}
精简
@Service
public class UserService {
public void createUser(UserCreateVO create, OpUserVO user) {
checkOperatorUser(user);
...
}
private void checkOperatorUser(OpUserVO user) {
if (!hasPermission(user)) {
throw new BusinessRuntimeException("用户无操作权限");
}
...
}
...
}
@RestController
@RequestMapping("/user")
public class UserController {
@Autowired
private UserService userService;
@PostMapping("/createUser")
public Result<Void> createUser(@RequestBody @Valid UserCreateVO create, OpUserVO user) {
userService.createUser(create, user);
return Result.success();
}
...
}
利用注解
利用 Lombok 注解
普通
public class UserVO {
private Long id;
private String name;
public Long getId() {
return this.id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
...
}
精简
@Getter
@Setter
@ToString
public class UserVO {
private Long id;
private String name;
...
}
利用 Validation 注解
普通
@Data
public class UserCreateVO {
private String name;
private Long companyId;
}
@Service
public class UserService {
public Long createUser(UserCreateVO create) {
// TODO: 创建用户
if(create.getName()==null){
...
}
if(create.getCompanyId()==null){
...
}
return null;
}
}
精简
@Getter
@Setter
@ToString
public class UserCreateVO {
@NotBlank(message = "用户名称不能为空")
private String name;
@NotNull(message = "公司标识不能为空")
private Long companyId;
...
}
@Service
@Validated
public class UserService {
public Long createUser(@Valid UserCreateVO create) {
// TODO: 创建用户
return null;
}
}
利用 @NonNull 注解
普通
public List<UserVO> queryCompanyUser(Long companyId) {
// 检查公司标识
if (companyId == null) {
return null;
}
// 查询返回用户
List<UserDO> userList = userDAO.queryByCompanyId(companyId);
return userList.stream().map(this::transUser).collect(Collectors.toList());
}
Long companyId = 1L;
List<UserVO> userList = queryCompanyUser(companyId);
if (CollectionUtils.isNotEmpty(userList)) {
for (UserVO user : userList) {
// TODO: 处理公司用户
}
}
精简
public @NonNull List<UserVO> queryCompanyUser(@NonNull Long companyId) {
List<UserDO> userList = userDAO.queryByCompanyId(companyId);
return userList.stream().map(this::transUser).collect(Collectors.toList());
}
Long companyId = 1L;
List<UserVO> userList = queryCompanyUser(companyId);
for (UserVO user : userList) {
// TODO: 处理公司用户
}
利用注解特性
注解有以下特性可用于精简注解声明： 1、当注解属性值跟默认值一致时，可以删除该属性赋值； 2、当注解只有value属性时，可以去掉value进行简写； 3、当注解属性组合等于另一个特定注解时，直接采用该特定注解。
普通
@Lazy(true);
@Service(value = "userService")
@RequestMapping(path = "/getUser", method = RequestMethod.GET)
精简
@Lazy
@Service("userService")
@GetMapping("/getUser")
利用泛型
泛型接口
普通
public interface Comparable {
public int compareTo(Object other);
}
@Getter
@Setter
@ToString
public class UserVO implements Comparable {
private Long id;
@Override
public int compareTo(Object other) {
UserVO user = (UserVO)other;
return Long.compare(this.id, user.id);
}
}
精简
public interface Comparable<T> {
public int compareTo(T other);
}
@Getter
@Setter
@ToString
public class UserVO implements Comparable<UserVO> {
private Long id;
@Override
public int compareTo(UserVO other) {
return Long.compare(this.id, other.id);
}
}
泛型类
普通
@Getter
@Setter
@ToString
public class IntPoint {
private Integer x;
private Integer y;
}
@Getter
@Setter
@ToString
public class DoublePoint {
private Double x;
private Double y;
}
精简
@Getter
@Setter
@ToString
public class Point<T extends Number> {
private T x;
private T y;
}
泛型方法
普通
public static Map<String, Integer> newHashMap(String[] keys, Integer[] values) {
// 检查参数非空
if (ArrayUtils.isEmpty(keys) || ArrayUtils.isEmpty(values)) {
return Collections.emptyMap();
}
// 转化哈希映射
Map<String, Integer> map = new HashMap<>();
int length = Math.min(keys.length, values.length);
for (int i = 0; i < length; i++) {
map.put(keys[i], values[i]);
}
return map;
}
精简
public static <K, V> Map<K, V> newHashMap(K[] keys, V[] values) {
// 检查参数非空
if (ArrayUtils.isEmpty(keys) || ArrayUtils.isEmpty(values)) {
return Collections.emptyMap();
}
// 转化哈希映射
Map<K, V> map = new HashMap<>();
int length = Math.min(keys.length, values.length);
for (int i = 0; i < length; i++) {
map.put(keys[i], values[i]);
}
return map;
}
利用自身方法
利用构造方法
@Getter
@Setter
@ToString
public class PageDataVO<T> {
private Long totalCount;
private List<T> dataList;
}
PageDataVO<UserVO> pageData = new PageDataVO<>();
pageData.setTotalCount(totalCount);
pageData.setDataList(userList);
return pageData;
精简
@Getter
@Setter
@ToString
@NoArgsConstructor
@AllArgsConstructor
public class PageDataVO<T> {
private Long totalCount;
private List<T> dataList;
}
return new PageDataVO<>(totalCount, userList);
- 注意：如果属性字段被替换时，存在构造函数初始化赋值问题。比如把属性字段title替换为 nickname ，由于构造函数的参数个数和类型不变，原有构造函数初始化语句不会报错，导致把原title值赋值给 nickname 。如果采用 Setter 方法赋值，编译器会提示错误并要求修复。
利用 Set 的 add 方法
普通
以下案例是进行用户去重转化操作，需要先调用 contains 方法判断存在，后调用add方法进行添加。
Set<Long> userIdSet = new HashSet<>();
List<UserVO> userVOList = new ArrayList<>();
for (UserDO userDO : userDOList) {
if (!userIdSet.contains(userDO.getId())) {
userIdSet.add(userDO.getId());
userVOList.add(transUser(userDO));
}
}
精简
SSet<Long> userIdSet = new HashSet<>();
List<UserVO> userVOList = new ArrayList<>();
for (UserDO userDO : userDOList) {
if (userIdSet.add(userDO.getId())) {
userVOList.add(transUser(userDO));
}
}
利用 Map 的 computeIfAbsent 方法
普通
Map<Long, List<UserDO>> roleUserMap = new HashMap<>();
for (UserDO userDO : userDOList) {
Long roleId = userDO.getRoleId();
List<UserDO> userList = roleUserMap.get(roleId);
if (Objects.isNull(userList)) {
userList = new ArrayList<>();
roleUserMap.put(roleId, userList);
}
userList.add(userDO);
}
精简
Map<Long, List<UserDO>> roleUserMap = new HashMap<>();
for (UserDO userDO : userDOList) {
roleUserMap.computeIfAbsent(userDO.getRoleId(), key -> new ArrayList<>())
.add(userDO);
}
利用链式编程
普通
StringBuilder builder = new StringBuilder(96);
builder.append("select id, name from ");
builder.append(T_USER);
builder.append(" where id = ");
builder.append(userId);
builder.append(";");
精简
StringBuilder builder = new StringBuilder(96);
builder.append("select id, name from ")
.append(T_USER)
.append(" where id = ")
.append(userId)
.append(";");
利用工具方法
避免空值判断
普通
if (userList != null && !userList.isEmpty()) {
// TODO: 处理代码
}
精简
if (CollectionUtils.isNotEmpty(userList)) {
// TODO: 处理代码
}
避免条件判断
普通
double result;
if (value <= MIN_LIMIT) {
result = MIN_LIMIT;
} else {
result = value;
}
精简
double result = Math.max(MIN_LIMIT, value);
简化赋值语句
普通
public static final List<String> ANIMAL_LIST;
static {
List<String> animalList = new ArrayList<>();
animalList.add("dog");
animalList.add("cat");
animalList.add("tiger");
ANIMAL_LIST = Collections.unmodifiableList(animalList);
}
精简
// JDK流派
public static final List<String> ANIMAL_LIST = Arrays.asList("dog", "cat", "tiger");
// Guava流派
public static final List<String> ANIMAL_LIST = ImmutableList.of("dog", "cat", "tiger");
- 注意：Arrays.asList 返回的 List 并不是 ArrayList ，不支持 add 等变更操作。
简化数据拷贝
普通
UserVO userVO = new UserVO();
userVO.setId(userDO.getId());
userVO.setName(userDO.getName());
...
userVO.setDescription(userDO.getDescription());
userVOList.add(userVO);
精简
UserVO userVO = new UserVO();
BeanUtils.copyProperties(userDO, userVO);
userVOList.add(userVO);
反例
List<UserVO> userVOList = JSON.parseArray(JSON.toJSONString(userDOList), UserVO.class);
- 精简代码，但不能以过大的性能损失为代价。例子是浅层拷贝，用不着 JSON 这样重量级的武器。
简化异常断言
普通
if (Objects.isNull(userId)) {
throw new IllegalArgumentException("用户标识不能为空");
}
精简
Assert.notNull(userId, "用户标识不能为空");
- 注意：可能有些插件不认同这种判断，导致使用该对象时会有空指针警告。
简化测试用例
普通
@Test
public void testCreateUser() {
UserCreateVO userCreate = new UserCreateVO();
userCreate.setName("Changyi");
userCreate.setTitle("Developer");
userCreate.setCompany("AMAP");
...
Long userId = userService.createUser(OPERATOR, userCreate);
Assert.assertNotNull(userId, "创建用户失败");
}
精简
@Test
public void testCreateUser() {
String jsonText = ResourceHelper.getResourceAsString(getClass(), "createUser.json");
UserCreateVO userCreate = JSON.parseObject(jsonText, UserCreateVO.class);
Long userId = userService.createUser(OPERATOR, userCreate);
Assert.assertNotNull(userId, "创建用户失败");
}
- 建议：JSON 文件名最好以被测试的方法命名，如果有多个版本可以用数字后缀表示。
简化算法实现
普通
int totalSize = valueList.size();
List<List<Integer>> partitionList = new ArrayList<>();
for (int i = 0; i < totalSize; i += PARTITION_SIZE) {
partitionList.add(valueList.subList(i, Math.min(i + PARTITION_SIZE, totalSize)));
}
精简
List<List<Integer>> partitionList = ListUtils.partition(valueList, PARTITION_SIZE);
封装工具方法
普通
比如，SQL 设置参数值的方法就比较难用，setLong 方法不能设置参数值为 null 。
// 设置参数值
if (Objects.nonNull(user.getId())) {
statement.setLong(1, user.getId());
} else {
statement.setNull(1, Types.BIGINT);
}
精简 我们可以封装为一个工具类 SqlHelper ，简化设置参数值的代码。
/** SQL辅助类 */
public final class SqlHelper {
/** 设置长整数值 */
public static void setLong(PreparedStatement statement, int index, Long value) throws SQLException {
if (Objects.nonNull(value)) {
statement.setLong(index, value.longValue());
} else {
statement.setNull(index, Types.BIGINT);
}
}
...
}
// 设置参数值
SqlHelper.setLong(statement, 1, user.getId());
利用数据结构
利用数组简化
public static int getGrade(double score) {
if (score >= 90.0D) {
return 1;
}
if (score >= 80.0D) {
return 2;
}
if (score >= 60.0D) {
return 3;
}
if (score >= 30.0D) {
return 4;
}
return 5;
}
精简
private static final double[] SCORE_RANGES = new double[] {90.0D, 80.0D, 60.0D, 30.0D};
public static int getGrade(double score) {
for (int i = 0; i < SCORE_RANGES.length; i++) {
if (score >= SCORE_RANGES[i]) {
return i + 1;
}
}
return SCORE_RANGES.length + 1;
}
思考：上面的案例返回值是递增的，所以用数组简化是没有问题的。但是，如果返回值不是递增的，能否用数组进行简化呢？答案是可以的，请自行思考解决。
利用 Map 简化
普通
public static String getBiologyClass(String name) {
switch (name) {
case "dog" :
return "animal";
case "cat" :
return "animal";
case "lavender" :
return "plant";
...
default :
return null;
}
}
精简
private static final Map<String, String> BIOLOGY_CLASS_MAP
= ImmutableMap.<String, String>builder()
.put("dog", "animal")
.put("cat", "animal")
.put("lavender", "plant")
...
.build();
public static String getBiologyClass(String name) {
return BIOLOGY_CLASS_MAP.get(name);
}
已经把方法简化为一行代码，其实都没有封装方法的必要了。
利用容器类简化
普通
@Setter
@Getter
@ToString
@AllArgsConstructor
public static class PointAndDistance {
private Point point;
private Double distance;
}
public static PointAndDistance getNearest(Point point, Point[] points) {
// 计算最近点和距离
...
// 返回最近点和距离
return new PointAndDistance(nearestPoint, nearestDistance);
}
精简
public static Pair<Point, Double> getNearest(Point point, Point[] points) {
// 计算最近点和距离
...
// 返回最近点和距离
return ImmutablePair.of(nearestPoint, nearestDistance);
}
利用 ThreadLocal 简化
普通
由于 DateFormat 的 format 方法线程非安全（建议使用替代方法），在线程中频繁初始化 DateFormat 性能太低，如果考虑重用只能用参数传入 DateFormat 。例子如下：
public static String formatDate(Date date, DateFormat format) {
return format.format(date);
}
public static List<String> getDateList(Date minDate, Date maxDate, DateFormat format) {
List<String> dateList = new ArrayList<>();
Calendar calendar = Calendar.getInstance();
calendar.setTime(minDate);
String currDate = formatDate(calendar.getTime(), format);
String maxsDate = formatDate(maxDate, format);
while (currDate.compareTo(maxsDate) <= 0) {
dateList.add(currDate);
calendar.add(Calendar.DATE, 1);
currDate = formatDate(calendar.getTime(), format);
}
return dateList;
}
精简
可能你会觉得以下的代码量反而多了，如果调用工具方法的地方比较多，就可以省下一大堆 DateFormat 初始化和传入参数的代码。
private static final ThreadLocal<DateFormat> LOCAL_DATE_FORMAT = new ThreadLocal<DateFormat>() {
@Override
protected DateFormat initialValue() {
return new SimpleDateFormat("yyyyMMdd");
}
};
public static String formatDate(Date date) {
return LOCAL_DATE_FORMAT.get().format(date);
}
public static List<String> getDateList(Date minDate, Date maxDate) {
List<String> dateList = new ArrayList<>();
Calendar calendar = Calendar.getInstance();
calendar.setTime(minDate);
String currDate = formatDate(calendar.getTime());
String maxsDate = formatDate(maxDate);
while (currDate.compareTo(maxsDate) <= 0) {
dateList.add(currDate);
calendar.add(Calendar.DATE, 1);
currDate = formatDate(calendar.getTime());
}
return dateList;
}
- 注意：ThreadLocal 有一定的内存泄露的风险，尽量在业务代码结束前调用 remove 方法进行数据清除。
利用 Optional
普通
Integer thisValue;
if (Objects.nonNull(value)) {
thisValue = value;
} else {
thisValue = DEFAULT_VALUE;
}
精简
Integer thisValue = Optional.ofNullable(value).orElse(DEFAULT_VALUE);
保证值合法
普通
Integer thisValue;
if (Objects.nonNull(value) && value.compareTo(MAX_VALUE) <= 0) {
thisValue = value;
} else {
thisValue = MAX_VALUE;
}
精简
Integer thisValue = Optional.ofNullable(value)
.filter(tempValue -> tempValue.compareTo(MAX_VALUE) <= 0).orElse(MAX_VALUE);
避免空判断
普通
String zipcode = null;
if (Objects.nonNull(user)) {
Address address = user.getAddress();
if (Objects.nonNull(address)) {
Country country = address.getCountry();
if (Objects.nonNull(country)) {
zipcode = country.getZipcode();
}
}
}
精简
String zipcode = Optional.ofNullable(user).map(User::getAddress)
.map(Address::getCountry).map(Country::getZipcode).orElse(null);
利用 Stream
普通
boolean isFound = false;
for (UserDO user : userList) {
if (Objects.equals(user.getId(), userId)) {
isFound = true;
break;
}
}
精简
boolean isFound = userList.stream()
.anyMatch(user -> Objects.equals(user.getId(), userId));
过滤集合数据
普通
List<UserDO> resultList = new ArrayList<>();
for (UserDO user : userList) {
if (Boolean.TRUE.equals(user.getIsSuper())) {
resultList.add(user);
}
}
精简
List<UserDO> resultList = userList.stream()
.filter(user -> Boolean.TRUE.equals(user.getIsSuper()))
.collect(Collectors.toList());
汇总集合数据
普通
double total = 0.0D;
for (Account account : accountList) {
total += account.getBalance();
}
精简
double total = accountList.stream().mapToDouble(Account::getBalance).sum();
转化集合数据
普通
List<UserVO> userVOList = new ArrayList<>();
for (UserDO userDO : userDOList) {
userVOList.add(transUser(userDO));
}
精简
List<UserVO> userVOList = userDOList.stream()
.map(this::transUser).collect(Collectors.toList());
分组集合数据
普通
Map<Long, List<UserDO>> roleUserMap = new HashMap<>();
for (UserDO userDO : userDOList) {
roleUserMap.computeIfAbsent(userDO.getRoleId(), key -> new ArrayList<>())
.add(userDO);
}
精简
Map<Long, List<UserDO>> roleUserMap = userDOList.stream()
.collect(Collectors.groupingBy(UserDO::getRoleId));
分组汇总集合
普通
Map<Long, Double> roleTotalMap = new HashMap<>();
for (Account account : accountList) {
Long roleId = account.getRoleId();
Double total = Optional.ofNullable(roleTotalMap.get(roleId)).orElse(0.0D);
roleTotalMap.put(roleId, total + account.getBalance());
}
精简
roleTotalMap = accountList.stream().collect(Collectors.groupingBy(Account::getRoleId, Collectors.summingDouble(Account::getBalance)));
生成范围集合
普通
int[] array1 = new int[N];
for (int i = 0; i < N; i++) {
array1[i] = i + 1;
}
int[] array2 = new int[N];
array2[0] = 1;
for (int i = 1; i < N; i++) {
array2[i] = array2[i - 1] * 2;
}
精简
int[] array1 = IntStream.rangeClosed(1, N).toArray();
int[] array2 = IntStream.iterate(1, n -> n * 2).limit(N).toArray();
利用程序结构
返回条件表达式
普通
public boolean isSuper(Long userId)
UserDO user = userDAO.get(userId);
if (Objects.nonNull(user) && Boolean.TRUE.equals(user.getIsSuper())) {
return true;
}
return false;
}
精简
public boolean isSuper(Long userId)
UserDO user = userDAO.get(userId);
return Objects.nonNull(user) && Boolean.TRUE.equals(user.getIsSuper());
}
最小化条件作用域
普通
Result result = summaryService.reportWorkDaily(workDaily);
if (result.isSuccess()) {
String message = "上报工作日报成功";
dingtalkService.sendMessage(user.getPhone(), message);
} else {
String message = "上报工作日报失败:" + result.getMessage();
log.warn(message);
dingtalkService.sendMessage(user.getPhone(), message);
}
精简
String message;
Result result = summaryService.reportWorkDaily(workDaily);
if (result.isSuccess()) {
message = "上报工作日报成功";
} else {
message = "上报工作日报失败:" + result.getMessage();
log.warn(message);
}
dingtalkService.sendMessage(user.getPhone(), message);
调整表达式位置
普通1
String line = readLine();
while (Objects.nonNull(line)) {
... // 处理逻辑代码
line = readLine();
}
普通2
for (String line = readLine(); Objects.nonNull(line); line = readLine()) {
... // 处理逻辑代码
}
精简
String line;
while (Objects.nonNull(line = readLine())) {
... // 处理逻辑代码
}
- 注意：有些规范可能不建议这种精简写法。
利用非空对象
普通
private static final int MAX_VALUE = 1000;
boolean isMax = (value != null && value.equals(MAX_VALUE));
boolean isTrue = (result != null && result.equals(Boolean.TRUE));
精简
private static final Integer MAX_VALUE = 1000;
boolean isMax = MAX_VALUE.equals(value);
boolean isTrue = Boolean.TRUE.equals(result);
利用设计模式
模板方法模式
普通
@Repository
public class UserValue {
/** 值操作 */
@Resource(name = "stringRedisTemplate")
private ValueOperations<String, String> valueOperations;
/** 值模式 */
private static final String KEY_FORMAT = "Value:User:%s";
/** 设置值 */
public void set(Long id, UserDO value) {
String key = String.format(KEY_FORMAT, id);
valueOperations.set(key, JSON.toJSONString(value));
}
/** 获取值 */
public UserDO get(Long id) {
String key = String.format(KEY_FORMAT, id);
String value = valueOperations.get(key);
return JSON.parseObject(value, UserDO.class);
}
...
}
@Repository
public class RoleValue {
/** 值操作 */
@Resource(name = "stringRedisTemplate")
private ValueOperations<String, String> valueOperations;
/** 值模式 */
private static final String KEY_FORMAT = "Value:Role:%s";
/** 设置值 */
public void set(Long id, RoleDO value) {
String key = String.format(KEY_FORMAT, id);
valueOperations.set(key, JSON.toJSONString(value));
}
/** 获取值 */
public RoleDO get(Long id) {
String key = String.format(KEY_FORMAT, id);
String value = valueOperations.get(key);
return JSON.parseObject(value, RoleDO.class);
}
...
}
精简
public abstract class AbstractDynamicValue<I, V> {
/** 值操作 */
@Resource(name = "stringRedisTemplate")
private ValueOperations<String, String> valueOperations;
/** 设置值 */
public void set(I id, V value) {
valueOperations.set(getKey(id), JSON.toJSONString(value));
}
/** 获取值 */
public V get(I id) {
return JSON.parseObject(valueOperations.get(getKey(id)), getValueClass());
}
...
/** 获取主键 */
protected abstract String getKey(I id);
/** 获取值类 */
protected abstract Class<V> getValueClass();
}
@Repository
public class UserValue extends AbstractValue<Long, UserDO> {
/** 获取主键 */
@Override
protected String getKey(Long id) {
return String.format("Value:User:%s", id);
}
/** 获取值类 */
@Override
protected Class<UserDO> getValueClass() {
return UserDO.class;
}
}
@Repository
public class RoleValue extends AbstractValue<Long, RoleDO> {
/** 获取主键 */
@Override
protected String getKey(Long id) {
return String.format("Value:Role:%s", id);
}
/** 获取值类 */
@Override
protected Class<RoleDO> getValueClass() {
return RoleDO.class;
}
}
建造者模式
普通
public interface DataHandler<T> {
/** 解析数据 */
public T parseData(Record record);
/** 存储数据 */
public boolean storeData(List<T> dataList);
}
public <T> long executeFetch(String tableName, int batchSize, DataHandler<T> dataHandler) throws Exception {
// 构建下载会话
DownloadSession session = buildSession(tableName);
// 获取数据数量
long recordCount = session.getRecordCount();
if (recordCount == 0) {
return 0;
}
// 进行数据读取
long fetchCount = 0L;
try (RecordReader reader = session.openRecordReader(0L, recordCount, true)) {
// 依次读取数据
Record record;
List<T> dataList = new ArrayList<>(batchSize);
while ((record = reader.read()) != null) {
// 解析添加数据
T data = dataHandler.parseData(record);
if (Objects.nonNull(data)) {
dataList.add(data);
}
// 批量存储数据
if (dataList.size() == batchSize) {
boolean isContinue = dataHandler.storeData(dataList);
fetchCount += batchSize;
dataList.clear();
if (!isContinue) {
break;
}
}
}
// 存储剩余数据
if (CollectionUtils.isNotEmpty(dataList)) {
dataHandler.storeData(dataList);
fetchCount += dataList.size();
dataList.clear();
}
}
// 返回获取数量
return fetchCount;
}
// 使用案例
long fetchCount = odpsService.executeFetch("user", 5000, new DataHandler() {
/** 解析数据 */
@Override
public T parseData(Record record) {
UserDO user = new UserDO();
user.setId(record.getBigint("id"));
user.setName(record.getString("name"));
return user;
}
/** 存储数据 */
@Override
public boolean storeData(List<T> dataList) {
userDAO.batchInsert(dataList);
return true;
}
});
精简
public <T> long executeFetch(String tableName, int batchSize, Function<Record, T> dataParser, Function<List<T>, Boolean> dataStorage) throws Exception {
// 构建下载会话
DownloadSession session = buildSession(tableName);
// 获取数据数量
long recordCount = session.getRecordCount();
if (recordCount == 0) {
return 0;
}
// 进行数据读取
long fetchCount = 0L;
try (RecordReader reader = session.openRecordReader(0L, recordCount, true)) {
// 依次读取数据
Record record;
List<T> dataList = new ArrayList<>(batchSize);
while ((record = reader.read()) != null) {
// 解析添加数据
T data = dataParser.apply(record);
if (Objects.nonNull(data)) {
dataList.add(data);
}
// 批量存储数据
if (dataList.size() == batchSize) {
Boolean isContinue = dataStorage.apply(dataList);
fetchCount += batchSize;
dataList.clear();
if (!Boolean.TRUE.equals(isContinue)) {
break;
}
}
}
// 存储剩余数据
if (CollectionUtils.isNotEmpty(dataList)) {
dataStorage.apply(dataList);
fetchCount += dataList.size();
dataList.clear();
}
}
// 返回获取数量
return fetchCount;
}
// 使用案例
long fetchCount = odpsService.executeFetch("user", 5000, record -> {
UserDO user = new UserDO();
user.setId(record.getBigint("id"));
user.setName(record.getString("name"));
return user;
}, dataList -> {
userDAO.batchInsert(dataList);
return true;
});
普通的建造者模式，实现时需要定义 DataHandler 接口，调用时需要实现 DataHandler 匿名内部类，代码较多较繁琐。而精简后的建造者模式，充分利用了函数式编程，实现时无需定义接口，直接使用 Function 接口；调用时无需实现匿名内部类，直接采用 lambda 表达式，代码较少较简洁。
代理模式
普通
@Slf4j
@RestController
@RequestMapping("/user")
public class UserController {
/** 用户服务 */
@Autowired
private UserService userService;
/** 查询用户 */
@PostMapping("/queryUser")
public Result<?> queryUser(@RequestBody @Valid UserQueryVO query) {
try {
PageDataVO<UserVO> pageData = userService.queryUser(query);
return Result.success(pageData);
} catch (Exception e) {
log.error(e.getMessage(), e);
return Result.failure(e.getMessage());
}
}
...
}
精简1
基于 @ControllerAdvice 的异常处理：
@RestController
@RequestMapping("/user")
public class UserController {
/** 用户服务 */
@Autowired
private UserService userService;
/** 查询用户 */
@PostMapping("/queryUser")
public Result<PageDataVO<UserVO>> queryUser(@RequestBody @Valid UserQueryVO query) {
PageDataVO<UserVO> pageData = userService.queryUser(query);
return Result.success(pageData);
}
...
}
@Slf4j
@ControllerAdvice
public class GlobalControllerAdvice {
/** 处理异常 */
@ResponseBody
@ExceptionHandler(Exception.class)
public Result<Void> handleException(Exception e) {
log.error(e.getMessage(), e);
return Result.failure(e.getMessage());
}
}
精简2
基于 AOP 的异常处理：
// UserController代码同"精简1"
@Slf4j
@Aspect
public class WebExceptionAspect {
/** 点切面 */
@Pointcut("@annotation(org.springframework.web.bind.annotation.RequestMapping)")
private void webPointcut() {}
/** 处理异常 */
@AfterThrowing(pointcut = "webPointcut()", throwing = "e")
public void handleException(Exception e) {
Result<Void> result = Result.failure(e.getMessage());
writeContent(JSON.toJSONString(result));
}
...
}
利用删除代码
普通
import lombok.extern.slf4j.Slf4j;
@Slf4j
@Service
public class ProductService {
@Value("discardRate")
private double discardRate;
...
private ProductVO transProductDO(ProductDO productDO) {
ProductVO productVO = new ProductVO();
BeanUtils.copyProperties(productDO, productVO);
// productVO.setPrice(getDiscardPrice(productDO.getPrice()));
return productVO;
}
private BigDecimal getDiscardPrice(BigDecimal originalPrice) {
...
}
}
精简
@Service
public class ProductService {
...
private ProductVO transProductDO(ProductDO productDO) {
ProductVO productVO = new ProductVO();
BeanUtils.copyProperties(productDO, productVO);
return productVO;
}
}
删除接口方法的public
普通
public interface UserDAO {
public Long countUser(@Param("query") UserQuery query);
public List<UserDO> queryUser(@Param("query") UserQuery query);
}
精简
public interface UserDAO {
Long countUser(@Param("query") UserQuery query);
List<UserDO> queryUser(@Param("query") UserQuery query);
}
删除枚举构造方法的 private
普通
public enum UserStatus {
DISABLED(0, "禁用"),
ENABLED(1, "启用");
private final Integer value;
private final String desc;
private UserStatus(Integer value, String desc) {
this.value = value;
this.desc = desc;
}
...
}
精简
public enum UserStatus {
DISABLED(0, "禁用"),
ENABLED(1, "启用");
private final Integer value;
private final String desc;
UserStatus(Integer value, String desc) {
this.value = value;
this.desc = desc;
}
...
}
删除 final 类方法的 final
普通
public final Rectangle implements Shape {
...
@Override
public final double getArea() {
return width * height;
}
}
精简
public final Rectangle implements Shape {
...
@Override
public double getArea() {
return width * height;
}
}
删除基类 implements 的接口
普通
public interface Shape {
...
double getArea();
}
public abstract AbstractShape implements Shape {
...
}
public final Rectangle extends AbstractShape implements Shape {
...
@Override
public double getArea() {
return width * height;
}
}
精简
...
public final Rectangle extends AbstractShape {
...
@Override
public double getArea() {
return width * height;
}
}
删除不必要的变量
普通
public Boolean existsUser(Long userId) {
Boolean exists = userDAO.exists(userId);
return exists;
}
精简
public Boolean existsUser(Long userId) {
return userDAO.exists(userId);
}