一、編程式事務

1.在執行事務提交或者回滾之前，事務狀態不確定時，可以判斷一下事務是否已完成，避免重復提交或者回滾出現異常

舉例：

TransactionStatus transactionStatus =  platformTransactionManager.getTransaction(transactionDefinition);
if (!transactionStatus.isCompleted()) {
    platformTransactionManager.commit(transactionStatus);
}

?2.由于編程式事務不會自動提交或者回滾，我們可以在try-catch之后加一個finally，判斷事務未完成時，進行回滾，保證每個事務一定會結束

舉例：

TransactionStatus transactionStatus = platformTransactionManager.getTransaction(transactionDefinition);
try {
    ... ...
} catch (Exception ex) {
    ... ...
} finally {
    if (!transactionStatus.isCompleted()) {
        platformTransactionManager.rollback(transactionStatus);
    }
}

二、Stream

1.使用到的數據結構及模擬數據

import io.swagger.annotations.ApiModelProperty;
import lombok.Data;
import java.math.BigDecimal;
@Data
public class Student {
    @ApiModelProperty(value = "學生ID")
    private String studentId;
    @ApiModelProperty(value = "學生姓名")
    private String studentName;
    @ApiModelProperty(value = "學生性別，1-男，2-女")
    private String studentSex;
    @ApiModelProperty(value = "學生年齡Integer")
    private Integer studentAgeInt;
    @ApiModelProperty(value = "學生年齡Double")
    private Double studentAgeDou;
    @ApiModelProperty(value = "學生年齡BigDecimal")
    private BigDecimal studentAgeDec;
}

// 數據列表 List
List<Student> studentList = new ArrayList<>();
Student student = new Student();
student.setStudentId("20220930000001");
student.setStudentName("趙甲");
student.setStudentSex("1");
student.setStudentAgeInt(11);
student.setStudentAgeDou(11.11);
student.setStudentAgeDec(new BigDecimal(11.11));
studentList.add(student);
student = new Student();
student.setStudentId("20220930000002");
student.setStudentName("錢乙");
student.setStudentSex("2");
student.setStudentAgeInt(12);
student.setStudentAgeDou(12.12);
student.setStudentAgeDec(new BigDecimal(12.12));
studentList.add(student);
student = new Student();
student.setStudentId("20220930000003");
student.setStudentName("孫丙");
student.setStudentSex("1");
student.setStudentAgeInt(13);
student.setStudentAgeDou(13.13);
student.setStudentAgeDec(new BigDecimal(13.13));
studentList.add(student);
student = new Student();
student.setStudentId("20220930000004");
student.setStudentName("李丁");
student.setStudentSex("2");
student.setStudentAgeInt(14);
student.setStudentAgeDou(14.14);
student.setStudentAgeDec(new BigDecimal(14.14));
studentList.add(student);
student = new Student();
student.setStudentId("20220930000005");
student.setStudentName("周戊");
student.setStudentSex("1");
student.setStudentAgeInt(15);
student.setStudentAgeDou(15.15);
student.setStudentAgeDec(new BigDecimal(15.15));
studentList.add(student);

// 數據Map
Map<String,Student> studentMap = new HashMap<>(5);
Student student = new Student();
student.setStudentId("20220930000001");
student.setStudentName("趙甲");
student.setStudentSex("1");
student.setStudentAgeInt(11);
student.setStudentAgeDou(11.11);
student.setStudentAgeDec(new BigDecimal(11.11));
studentMap.put(student.getStudentId(),student);
student = new Student();
student.setStudentId("20220930000002");
student.setStudentName("錢乙");
student.setStudentSex("2");
student.setStudentAgeInt(12);
student.setStudentAgeDou(12.12);
student.setStudentAgeDec(new BigDecimal(12.12));
studentMap.put(student.getStudentId(),student);
student = new Student();
student.setStudentId("20220930000003");
student.setStudentName("孫丙");
student.setStudentSex("1");
student.setStudentAgeInt(13);
student.setStudentAgeDou(13.13);
student.setStudentAgeDec(new BigDecimal(13.13));
studentMap.put(student.getStudentId(),student);
student = new Student();
student.setStudentId("20220930000004");
student.setStudentName("李丁");
student.setStudentSex("2");
student.setStudentAgeInt(14);
student.setStudentAgeDou(14.14);
student.setStudentAgeDec(new BigDecimal(14.14));
studentMap.put(student.getStudentId(),student);
student = new Student();
student.setStudentId("20220930000005");
student.setStudentName("周戊");
student.setStudentSex("1");
student.setStudentAgeInt(15);
student.setStudentAgeDou(15.15);
student.setStudentAgeDec(new BigDecimal(15.15));
studentMap.put(student.getStudentId(),student);

?2.過濾-filter

// 過濾所有女生
List<Student> studentListT = studentList.stream()
        .filter(item -> "2".equals(item.getStudentSex())).collect(Collectors.toList());
// 過濾12歲以上學生（3種數據類型示例）
studentListT = studentList.stream().filter(item -> item.getStudentAgeInt() > 12).collect(Collectors.toList());
studentListT = studentList.stream().filter(item -> item.getStudentAgeDou() > 12).collect(Collectors.toList());
studentListT = studentList.stream()
        .filter(item -> item.getStudentAgeDec().compareTo(new BigDecimal(12)) > 0).collect(Collectors.toList());
// 過濾12歲以上男生（2種方法示例）
studentListT = studentList.stream().filter(item -> "1".equals(item.getStudentSex()))
        .filter(item -> item.getStudentAgeInt() > 12).collect(Collectors.toList());
studentListT = studentList.stream()
        .filter(item -> "1".equals(item.getStudentSex()) && item.getStudentAgeInt() > 12).collect(Collectors.toList());

三、Map轉對象

最近，研究map與java對象之間的相互轉換，總結了5種方法

https://www.likecs.net/article/190478.htm

四、Linux常用命令

1.查看所有java進程

ps -ef | grep java

2.結束某個進程

kill -9 pid